    /*
        pybind11/pytypes.h: Convenience wrapper classes for basic Python types

        Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>

        All rights reserved. Use of this source code is governed by a
        BSD-style license that can be found in the LICENSE file.
    */

    #pragma once

    #include "detail/common.h"
    #include "buffer_info.h"

    #include <assert.h>
    #include <cstddef>
    #include <exception>
    #include <frameobject.h>
    #include <iterator>
    #include <memory>
    #include <string>
    #include <type_traits>
    #include <typeinfo>
    #include <utility>

    #if defined(PYBIND11_HAS_OPTIONAL)
    #    include <optional>
    #endif

    #ifdef PYBIND11_HAS_STRING_VIEW
    #    include <string_view>
    #endif

    PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)

    PYBIND11_WARNING_DISABLE_MSVC(4127)

    /* A few forward declarations */
    class handle;
    class object;
    class str;
    class iterator;
    class type;
    struct arg;
    struct arg_v;

    PYBIND11_NAMESPACE_BEGIN(detail)
    class args_proxy;
    bool isinstance_generic(handle obj, const std::type_info &tp);

    // Accessor forward declarations
    template <typename Policy>
    class accessor;
    namespace accessor_policies {
    struct obj_attr;
    struct str_attr;
    struct generic_item;
    struct sequence_item;
    struct list_item;
    struct tuple_item;
    } // namespace accessor_policies
    // PLEASE KEEP handle_type_name SPECIALIZATIONS IN SYNC.
    using obj_attr_accessor = accessor<accessor_policies::obj_attr>;
    using str_attr_accessor = accessor<accessor_policies::str_attr>;
    using item_accessor = accessor<accessor_policies::generic_item>;
    using sequence_accessor = accessor<accessor_policies::sequence_item>;
    using list_accessor = accessor<accessor_policies::list_item>;
    using tuple_accessor = accessor<accessor_policies::tuple_item>;

    /// Tag and check to identify a class which implements the Python object API
    class pyobject_tag {};
    template <typename T>
    using is_pyobject = std::is_base_of<pyobject_tag, remove_reference_t<T>>;

    /** \rst
        A mixin class which adds common functions to `handle`, `object` and various accessors.
        The only requirement for `Derived` is to implement ``PyObject *Derived::ptr() const``.
    \endrst */
    template <typename Derived>
    class object_api : public pyobject_tag {
        const Derived &derived() const { return static_cast<const Derived &>(*this); }

    public:
        /** \rst
            Return an iterator equivalent to calling ``iter()`` in Python. The object
            must be a collection which supports the iteration protocol.
        \endrst */
        iterator begin() const;
        /// Return a sentinel which ends iteration.
        iterator end() const;

        /** \rst
            Return an internal functor to invoke the object's sequence protocol. Casting
            the returned ``detail::item_accessor`` instance to a `handle` or `object`
            subclass causes a corresponding call to ``__getitem__``. Assigning a `handle`
            or `object` subclass causes a call to ``__setitem__``.
        \endrst */
        item_accessor operator[](handle key) const;
        /// See above (the only difference is that the key's reference is stolen)
        item_accessor operator[](object &&key) const;
        /// See above (the only difference is that the key is provided as a string literal)
        item_accessor operator[](const char *key) const;

        /** \rst
            Return an internal functor to access the object's attributes. Casting the
            returned ``detail::obj_attr_accessor`` instance to a `handle` or `object`
            subclass causes a corresponding call to ``getattr``. Assigning a `handle`
            or `object` subclass causes a call to ``setattr``.
        \endrst */
        obj_attr_accessor attr(handle key) const;
        /// See above (the only difference is that the key's reference is stolen)
        obj_attr_accessor attr(object &&key) const;
        /// See above (the only difference is that the key is provided as a string literal)
        str_attr_accessor attr(const char *key) const;

        /** \rst
            Matches * unpacking in Python, e.g. to unpack arguments out of a ``tuple``
            or ``list`` for a function call. Applying another * to the result yields
            ** unpacking, e.g. to unpack a dict as function keyword arguments.
            See :ref:`calling_python_functions`.
        \endrst */
        args_proxy operator*() const;

        /// Check if the given item is contained within this object, i.e. ``item in obj``.
        template <typename T>
        bool contains(T &&item) const;

        /** \rst
            Assuming the Python object is a function or implements the ``__call__``
            protocol, ``operator()`` invokes the underlying function, passing an
            arbitrary set of parameters. The result is returned as a `object` and
            may need to be converted back into a Python object using `handle::cast()`.

            When some of the arguments cannot be converted to Python objects, the
            function will throw a `cast_error` exception. When the Python function
            call fails, a `error_already_set` exception is thrown.
        \endrst */
        template <return_value_policy policy = return_value_policy::automatic_reference,
                  typename... Args>
        object operator()(Args &&...args) const;
        template <return_value_policy policy = return_value_policy::automatic_reference,
                  typename... Args>
        PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
        object call(Args &&...args) const;

        /// Equivalent to ``obj is other`` in Python.
        bool is(object_api const &other) const { return derived().ptr() == other.derived().ptr(); }
        /// Equivalent to ``obj is None`` in Python.
        bool is_none() const { return derived().ptr() == Py_None; }
        /// Equivalent to obj == other in Python
        bool equal(object_api const &other) const { return rich_compare(other, Py_EQ); }
        bool not_equal(object_api const &other) const { return rich_compare(other, Py_NE); }
        bool operator<(object_api const &other) const { return rich_compare(other, Py_LT); }
        bool operator<=(object_api const &other) const { return rich_compare(other, Py_LE); }
        bool operator>(object_api const &other) const { return rich_compare(other, Py_GT); }
        bool operator>=(object_api const &other) const { return rich_compare(other, Py_GE); }

        object operator-() const;
        object operator~() const;
        object operator+(object_api const &other) const;
        object operator+=(object_api const &other);
        object operator-(object_api const &other) const;
        object operator-=(object_api const &other);
        object operator*(object_api const &other) const;
        object operator*=(object_api const &other);
        object operator/(object_api const &other) const;
        object operator/=(object_api const &other);
        object operator|(object_api const &other) const;
        object operator|=(object_api const &other);
        object operator&(object_api const &other) const;
        object operator&=(object_api const &other);
        object operator^(object_api const &other) const;
        object operator^=(object_api const &other);
        object operator<<(object_api const &other) const;
        object operator<<=(object_api const &other);
        object operator>>(object_api const &other) const;
        object operator>>=(object_api const &other);

        PYBIND11_DEPRECATED("Use py::str(obj) instead")
        pybind11::str str() const;

        /// Get or set the object's docstring, i.e. ``obj.__doc__``.
        str_attr_accessor doc() const;

        /// Return the object's current reference count
        int ref_count() const { return static_cast<int>(Py_REFCNT(derived().ptr())); }

        // TODO PYBIND11_DEPRECATED(
        //     "Call py::type::handle_of(h) or py::type::of(h) instead of h.get_type()")
        handle get_type() const;

    private:
        bool rich_compare(object_api const &other, int value) const;
    };

    template <typename T>
    using is_pyobj_ptr_or_nullptr_t = detail::any_of<std::is_same<T, PyObject *>,
                                                     std::is_same<T, PyObject *const>,
                                                     std::is_same<T, std::nullptr_t>>;

    PYBIND11_NAMESPACE_END(detail)

    #if !defined(PYBIND11_HANDLE_REF_DEBUG) && !defined(NDEBUG)
    #    define PYBIND11_HANDLE_REF_DEBUG
    #endif

    /** \rst
        Holds a reference to a Python object (no reference counting)

        The `handle` class is a thin wrapper around an arbitrary Python object (i.e. a
        ``PyObject *`` in Python's C API). It does not perform any automatic reference
        counting and merely provides a basic C++ interface to various Python API functions.

        .. seealso::
            The `object` class inherits from `handle` and adds automatic reference
            counting features.
    \endrst */
    class handle : public detail::object_api<handle> {
    public:
        /// The default constructor creates a handle with a ``nullptr``-valued pointer
        handle() = default;

        /// Enable implicit conversion from ``PyObject *`` and ``nullptr``.
        /// Not using ``handle(PyObject *ptr)`` to avoid implicit conversion from ``0``.
        template <typename T,
                  detail::enable_if_t<detail::is_pyobj_ptr_or_nullptr_t<T>::value, int> = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        handle(T ptr) : m_ptr(ptr) {}

        /// Enable implicit conversion through ``T::operator PyObject *()``.
        template <
            typename T,
            detail::enable_if_t<detail::all_of<detail::none_of<std::is_base_of<handle, T>,
                                                               detail::is_pyobj_ptr_or_nullptr_t<T>>,
                                               std::is_convertible<T, PyObject *>>::value,
                                int>
            = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        handle(T &obj) : m_ptr(obj) {}

        /// Return the underlying ``PyObject *`` pointer
        PyObject *ptr() const { return m_ptr; }
        PyObject *&ptr() { return m_ptr; }

        /** \rst
            Manually increase the reference count of the Python object. Usually, it is
            preferable to use the `object` class which derives from `handle` and calls
            this function automatically. Returns a reference to itself.
        \endrst */
        const handle &inc_ref() const & {
    #ifdef PYBIND11_HANDLE_REF_DEBUG
            inc_ref_counter(1);
    #endif
    #ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
            if (m_ptr != nullptr && !PyGILState_Check()) {
                throw_gilstate_error("pybind11::handle::inc_ref()");
            }
    #endif
            Py_XINCREF(m_ptr);
            return *this;
        }

        /** \rst
            Manually decrease the reference count of the Python object. Usually, it is
            preferable to use the `object` class which derives from `handle` and calls
            this function automatically. Returns a reference to itself.
        \endrst */
        const handle &dec_ref() const & {
    #ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
            if (m_ptr != nullptr && !PyGILState_Check()) {
                throw_gilstate_error("pybind11::handle::dec_ref()");
            }
    #endif
            Py_XDECREF(m_ptr);
            return *this;
        }

        /** \rst
            Attempt to cast the Python object into the given C++ type. A `cast_error`
            will be throw upon failure.
        \endrst */
        template <typename T>
        T cast() const;
        /// Return ``true`` when the `handle` wraps a valid Python object
        explicit operator bool() const { return m_ptr != nullptr; }
        /** \rst
            Deprecated: Check that the underlying pointers are the same.
            Equivalent to ``obj1 is obj2`` in Python.
        \endrst */
        PYBIND11_DEPRECATED("Use obj1.is(obj2) instead")
        bool operator==(const handle &h) const { return m_ptr == h.m_ptr; }
        PYBIND11_DEPRECATED("Use !obj1.is(obj2) instead")
        bool operator!=(const handle &h) const { return m_ptr != h.m_ptr; }
        PYBIND11_DEPRECATED("Use handle::operator bool() instead")
        bool check() const { return m_ptr != nullptr; }

    protected:
        PyObject *m_ptr = nullptr;

    private:
    #ifdef PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF
        void throw_gilstate_error(const std::string &function_name) const {
            fprintf(
                stderr,
                "%s is being called while the GIL is either not held or invalid. Please see "
                "https://pybind11.readthedocs.io/en/stable/advanced/"
                "misc.html#common-sources-of-global-interpreter-lock-errors for debugging advice.\n"
                "If you are convinced there is no bug in your code, you can #define "
                "PYBIND11_NO_ASSERT_GIL_HELD_INCREF_DECREF "
                "to disable this check. In that case you have to ensure this #define is consistently "
                "used for all translation units linked into a given pybind11 extension, otherwise "
                "there will be ODR violations.",
                function_name.c_str());
            if (Py_TYPE(m_ptr)->tp_name != nullptr) {
                fprintf(stderr,
                        " The failing %s call was triggered on a %s object.",
                        function_name.c_str(),
                        Py_TYPE(m_ptr)->tp_name);
            }
            fprintf(stderr, "\n");
            fflush(stderr);
            throw std::runtime_error(function_name + " PyGILState_Check() failure.");
        }
    #endif

    #ifdef PYBIND11_HANDLE_REF_DEBUG
        static std::size_t inc_ref_counter(std::size_t add) {
            thread_local std::size_t counter = 0;
            counter += add;
            return counter;
        }

    public:
        static std::size_t inc_ref_counter() { return inc_ref_counter(0); }
    #endif
    };

    inline void set_error(const handle &type, const char *message) {
        PyErr_SetString(type.ptr(), message);
    }

    inline void set_error(const handle &type, const handle &value) {
        PyErr_SetObject(type.ptr(), value.ptr());
    }

    /** \rst
        Holds a reference to a Python object (with reference counting)

        Like `handle`, the `object` class is a thin wrapper around an arbitrary Python
        object (i.e. a ``PyObject *`` in Python's C API). In contrast to `handle`, it
        optionally increases the object's reference count upon construction, and it
        *always* decreases the reference count when the `object` instance goes out of
        scope and is destructed. When using `object` instances consistently, it is much
        easier to get reference counting right at the first attempt.
    \endrst */
    class object : public handle {
    public:
        object() = default;
        PYBIND11_DEPRECATED("Use reinterpret_borrow<object>() or reinterpret_steal<object>()")
        object(handle h, bool is_borrowed) : handle(h) {
            if (is_borrowed) {
                inc_ref();
            }
        }
        /// Copy constructor; always increases the reference count
        object(const object &o) : handle(o) { inc_ref(); }
        /// Move constructor; steals the object from ``other`` and preserves its reference count
        object(object &&other) noexcept : handle(other) { other.m_ptr = nullptr; }
        /// Destructor; automatically calls `handle::dec_ref()`
        ~object() { dec_ref(); }

        /** \rst
            Resets the internal pointer to ``nullptr`` without decreasing the
            object's reference count. The function returns a raw handle to the original
            Python object.
        \endrst */
        handle release() {
            PyObject *tmp = m_ptr;
            m_ptr = nullptr;
            return handle(tmp);
        }

        object &operator=(const object &other) {
            // Skip inc_ref and dec_ref if both objects are the same
            if (!this->is(other)) {
                other.inc_ref();
                // Use temporary variable to ensure `*this` remains valid while
                // `Py_XDECREF` executes, in case `*this` is accessible from Python.
                handle temp(m_ptr);
                m_ptr = other.m_ptr;
                temp.dec_ref();
            }
            return *this;
        }

        object &operator=(object &&other) noexcept {
            if (this != &other) {
                handle temp(m_ptr);
                m_ptr = other.m_ptr;
                other.m_ptr = nullptr;
                temp.dec_ref();
            }
            return *this;
        }

    #define PYBIND11_INPLACE_OP(iop)                                                                  \
        object iop(object_api const &other) { return operator=(handle::iop(other)); }

        PYBIND11_INPLACE_OP(operator+=)
        PYBIND11_INPLACE_OP(operator-=)
        PYBIND11_INPLACE_OP(operator*=)
        PYBIND11_INPLACE_OP(operator/=)
        PYBIND11_INPLACE_OP(operator|=)
        PYBIND11_INPLACE_OP(operator&=)
        PYBIND11_INPLACE_OP(operator^=)
        PYBIND11_INPLACE_OP(operator<<=)
        PYBIND11_INPLACE_OP(operator>>=)
    #undef PYBIND11_INPLACE_OP

        // Calling cast() on an object lvalue just copies (via handle::cast)
        template <typename T>
        T cast() const &;
        // Calling on an object rvalue does a move, if needed and/or possible
        template <typename T>
        T cast() &&;

    protected:
        // Tags for choosing constructors from raw PyObject *
        struct borrowed_t {};
        struct stolen_t {};

        /// @cond BROKEN
        template <typename T>
        friend T reinterpret_borrow(handle);
        template <typename T>
        friend T reinterpret_steal(handle);
        /// @endcond

    public:
        // Only accessible from derived classes and the reinterpret_* functions
        object(handle h, borrowed_t) : handle(h) { inc_ref(); }
        object(handle h, stolen_t) : handle(h) {}
    };

    /** \rst
        Declare that a `handle` or ``PyObject *`` is a certain type and borrow the reference.
        The target type ``T`` must be `object` or one of its derived classes. The function
        doesn't do any conversions or checks. It's up to the user to make sure that the
        target type is correct.

        .. code-block:: cpp

            PyObject *p = PyList_GetItem(obj, index);
            py::object o = reinterpret_borrow<py::object>(p);
            // or
            py::tuple t = reinterpret_borrow<py::tuple>(p); // <-- `p` must be already be a `tuple`
    \endrst */
    template <typename T>
    T reinterpret_borrow(handle h) {
        return {h, object::borrowed_t{}};
    }

    /** \rst
        Like `reinterpret_borrow`, but steals the reference.

         .. code-block:: cpp

            PyObject *p = PyObject_Str(obj);
            py::str s = reinterpret_steal<py::str>(p); // <-- `p` must be already be a `str`
    \endrst */
    template <typename T>
    T reinterpret_steal(handle h) {
        return {h, object::stolen_t{}};
    }

    PYBIND11_NAMESPACE_BEGIN(detail)

    // Equivalent to obj.__class__.__name__ (or obj.__name__ if obj is a class).
    inline const char *obj_class_name(PyObject *obj) {
        if (PyType_Check(obj)) {
            return reinterpret_cast<PyTypeObject *>(obj)->tp_name;
        }
        return Py_TYPE(obj)->tp_name;
    }

    std::string error_string();

    // The code in this struct is very unusual, to minimize the chances of
    // masking bugs (elsewhere) by errors during the error handling (here).
    // This is meant to be a lifeline for troubleshooting long-running processes
    // that crash under conditions that are virtually impossible to reproduce.
    // Low-level implementation alternatives are preferred to higher-level ones
    // that might raise cascading exceptions. Last-ditch-kind-of attempts are made
    // to report as much of the original error as possible, even if there are
    // secondary issues obtaining some of the details.
    struct error_fetch_and_normalize {
        // This comment only applies to Python <= 3.11:
        //     Immediate normalization is long-established behavior (starting with
        //     https://github.com/pybind/pybind11/commit/135ba8deafb8bf64a15b24d1513899eb600e2011
        //     from Sep 2016) and safest. Normalization could be deferred, but this could mask
        //     errors elsewhere, the performance gain is very minor in typical situations
        //     (usually the dominant bottleneck is EH unwinding), and the implementation here
        //     would be more complex.
        // Starting with Python 3.12, PyErr_Fetch() normalizes exceptions immediately.
        // Any errors during normalization are tracked under __notes__.
        explicit error_fetch_and_normalize(const char *called) {
            PyErr_Fetch(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
            if (!m_type) {
                pybind11_fail("Internal error: " + std::string(called)
                              + " called while "
                                "Python error indicator not set.");
            }
            const char *exc_type_name_orig = detail::obj_class_name(m_type.ptr());
            if (exc_type_name_orig == nullptr) {
                pybind11_fail("Internal error: " + std::string(called)
                              + " failed to obtain the name "
                                "of the original active exception type.");
            }
            m_lazy_error_string = exc_type_name_orig;
    #if PY_VERSION_HEX >= 0x030C0000
            // The presence of __notes__ is likely due to exception normalization
            // errors, although that is not necessarily true, therefore insert a
            // hint only:
            if (PyObject_HasAttrString(m_value.ptr(), "__notes__")) {
                m_lazy_error_string += "[WITH __notes__]";
            }
    #else
            // PyErr_NormalizeException() may change the exception type if there are cascading
            // failures. This can potentially be extremely confusing.
            PyErr_NormalizeException(&m_type.ptr(), &m_value.ptr(), &m_trace.ptr());
            if (m_type.ptr() == nullptr) {
                pybind11_fail("Internal error: " + std::string(called)
                              + " failed to normalize the "
                                "active exception.");
            }
            const char *exc_type_name_norm = detail::obj_class_name(m_type.ptr());
            if (exc_type_name_norm == nullptr) {
                pybind11_fail("Internal error: " + std::string(called)
                              + " failed to obtain the name "
                                "of the normalized active exception type.");
            }
    #    if defined(PYPY_VERSION_NUM) && PYPY_VERSION_NUM < 0x07030a00
            // This behavior runs the risk of masking errors in the error handling, but avoids a
            // conflict with PyPy, which relies on the normalization here to change OSError to
            // FileNotFoundError (https://github.com/pybind/pybind11/issues/4075).
            m_lazy_error_string = exc_type_name_norm;
    #    else
            if (exc_type_name_norm != m_lazy_error_string) {
                std::string msg = std::string(called)
                                  + ": MISMATCH of original and normalized "
                                    "active exception types: ";
                msg += "ORIGINAL ";
                msg += m_lazy_error_string;
                msg += " REPLACED BY ";
                msg += exc_type_name_norm;
                msg += ": " + format_value_and_trace();
                pybind11_fail(msg);
            }
    #    endif
    #endif
        }

        error_fetch_and_normalize(const error_fetch_and_normalize &) = delete;
        error_fetch_and_normalize(error_fetch_and_normalize &&) = delete;

        std::string format_value_and_trace() const {
            std::string result;
            std::string message_error_string;
            if (m_value) {
                auto value_str = reinterpret_steal<object>(PyObject_Str(m_value.ptr()));
                constexpr const char *message_unavailable_exc
                    = "<MESSAGE UNAVAILABLE DUE TO ANOTHER EXCEPTION>";
                if (!value_str) {
                    message_error_string = detail::error_string();
                    result = message_unavailable_exc;
                } else {
                    // Not using `value_str.cast<std::string>()`, to not potentially throw a secondary
                    // error_already_set that will then result in process termination (#4288).
                    auto value_bytes = reinterpret_steal<object>(
                        PyUnicode_AsEncodedString(value_str.ptr(), "utf-8", "backslashreplace"));
                    if (!value_bytes) {
                        message_error_string = detail::error_string();
                        result = message_unavailable_exc;
                    } else {
                        char *buffer = nullptr;
                        Py_ssize_t length = 0;
                        if (PyBytes_AsStringAndSize(value_bytes.ptr(), &buffer, &length) == -1) {
                            message_error_string = detail::error_string();
                            result = message_unavailable_exc;
                        } else {
                            result = std::string(buffer, static_cast<std::size_t>(length));
                        }
                    }
                }
    #if PY_VERSION_HEX >= 0x030B0000
                auto notes
                    = reinterpret_steal<object>(PyObject_GetAttrString(m_value.ptr(), "__notes__"));
                if (!notes) {
                    PyErr_Clear(); // No notes is good news.
                } else {
                    auto len_notes = PyList_Size(notes.ptr());
                    if (len_notes < 0) {
                        result += "\nFAILURE obtaining len(__notes__): " + detail::error_string();
                    } else {
                        result += "\n__notes__ (len=" + std::to_string(len_notes) + "):";
                        for (ssize_t i = 0; i < len_notes; i++) {
                            PyObject *note = PyList_GET_ITEM(notes.ptr(), i);
                            auto note_bytes = reinterpret_steal<object>(
                                PyUnicode_AsEncodedString(note, "utf-8", "backslashreplace"));
                            if (!note_bytes) {
                                result += "\nFAILURE obtaining __notes__[" + std::to_string(i)
                                          + "]: " + detail::error_string();
                            } else {
                                char *buffer = nullptr;
                                Py_ssize_t length = 0;
                                if (PyBytes_AsStringAndSize(note_bytes.ptr(), &buffer, &length)
                                    == -1) {
                                    result += "\nFAILURE formatting __notes__[" + std::to_string(i)
                                              + "]: " + detail::error_string();
                                } else {
                                    result += '\n';
                                    result += std::string(buffer, static_cast<std::size_t>(length));
                                }
                            }
                        }
                    }
                }
    #endif
            } else {
                result = "<MESSAGE UNAVAILABLE>";
            }
            if (result.empty()) {
                result = "<EMPTY MESSAGE>";
            }

            bool have_trace = false;
            if (m_trace) {
    #if !defined(PYPY_VERSION)
                auto *tb = reinterpret_cast<PyTracebackObject *>(m_trace.ptr());

                // Get the deepest trace possible.
                while (tb->tb_next) {
                    tb = tb->tb_next;
                }

                PyFrameObject *frame = tb->tb_frame;
                Py_XINCREF(frame);
                result += "\n\nAt:\n";
                while (frame) {
    #    if PY_VERSION_HEX >= 0x030900B1
                    PyCodeObject *f_code = PyFrame_GetCode(frame);
    #    else
                    PyCodeObject *f_code = frame->f_code;
                    Py_INCREF(f_code);
    #    endif
                    int lineno = PyFrame_GetLineNumber(frame);
                    result += "  ";
                    result += handle(f_code->co_filename).cast<std::string>();
                    result += '(';
                    result += std::to_string(lineno);
                    result += "): ";
                    result += handle(f_code->co_name).cast<std::string>();
                    result += '\n';
                    Py_DECREF(f_code);
    #    if PY_VERSION_HEX >= 0x030900B1
                    auto *b_frame = PyFrame_GetBack(frame);
    #    else
                    auto *b_frame = frame->f_back;
                    Py_XINCREF(b_frame);
    #    endif
                    Py_DECREF(frame);
                    frame = b_frame;
                }

                have_trace = true;
    #endif //! defined(PYPY_VERSION)
            }

            if (!message_error_string.empty()) {
                if (!have_trace) {
                    result += '\n';
                }
                result += "\nMESSAGE UNAVAILABLE DUE TO EXCEPTION: " + message_error_string;
            }

            return result;
        }

        std::string const &error_string() const {
            if (!m_lazy_error_string_completed) {
                m_lazy_error_string += ": " + format_value_and_trace();
                m_lazy_error_string_completed = true;
            }
            return m_lazy_error_string;
        }

        void restore() {
            if (m_restore_called) {
                pybind11_fail("Internal error: pybind11::detail::error_fetch_and_normalize::restore() "
                              "called a second time. ORIGINAL ERROR: "
                              + error_string());
            }
            PyErr_Restore(m_type.inc_ref().ptr(), m_value.inc_ref().ptr(), m_trace.inc_ref().ptr());
            m_restore_called = true;
        }

        bool matches(handle exc) const {
            return (PyErr_GivenExceptionMatches(m_type.ptr(), exc.ptr()) != 0);
        }

        // Not protecting these for simplicity.
        object m_type, m_value, m_trace;

    private:
        // Only protecting invariants.
        mutable std::string m_lazy_error_string;
        mutable bool m_lazy_error_string_completed = false;
        mutable bool m_restore_called = false;
    };

    inline std::string error_string() {
        return error_fetch_and_normalize("pybind11::detail::error_string").error_string();
    }

    PYBIND11_NAMESPACE_END(detail)

    /// Fetch and hold an error which was already set in Python.  An instance of this is typically
    /// thrown to propagate python-side errors back through C++ which can either be caught manually or
    /// else falls back to the function dispatcher (which then raises the captured error back to
    /// python).
    class PYBIND11_EXPORT_EXCEPTION error_already_set : public std::exception {
    public:
        /// Fetches the current Python exception (using PyErr_Fetch()), which will clear the
        /// current Python error indicator.
        error_already_set()
            : m_fetched_error{new detail::error_fetch_and_normalize("pybind11::error_already_set"),
                              m_fetched_error_deleter} {}

        /// The what() result is built lazily on demand.
        /// WARNING: This member function needs to acquire the Python GIL. This can lead to
        ///          crashes (undefined behavior) if the Python interpreter is finalizing.
        const char *what() const noexcept override;

        /// Restores the currently-held Python error (which will clear the Python error indicator first
        /// if already set).
        /// NOTE: This member function will always restore the normalized exception, which may or may
        ///       not be the original Python exception.
        /// WARNING: The GIL must be held when this member function is called!
        void restore() { m_fetched_error->restore(); }

        /// If it is impossible to raise the currently-held error, such as in a destructor, we can
        /// write it out using Python's unraisable hook (`sys.unraisablehook`). The error context
        /// should be some object whose `repr()` helps identify the location of the error. Python
        /// already knows the type and value of the error, so there is no need to repeat that.
        void discard_as_unraisable(object err_context) {
            restore();
            PyErr_WriteUnraisable(err_context.ptr());
        }
        /// An alternate version of `discard_as_unraisable()`, where a string provides information on
        /// the location of the error. For example, `__func__` could be helpful.
        /// WARNING: The GIL must be held when this member function is called!
        void discard_as_unraisable(const char *err_context) {
            discard_as_unraisable(reinterpret_steal<object>(PYBIND11_FROM_STRING(err_context)));
        }

        // Does nothing; provided for backwards compatibility.
        PYBIND11_DEPRECATED("Use of error_already_set.clear() is deprecated")
        void clear() {}

        /// Check if the currently trapped error type matches the given Python exception class (or a
        /// subclass thereof).  May also be passed a tuple to search for any exception class matches in
        /// the given tuple.
        bool matches(handle exc) const { return m_fetched_error->matches(exc); }

        const object &type() const { return m_fetched_error->m_type; }
        const object &value() const { return m_fetched_error->m_value; }
        const object &trace() const { return m_fetched_error->m_trace; }

    private:
        std::shared_ptr<detail::error_fetch_and_normalize> m_fetched_error;

        /// WARNING: This custom deleter needs to acquire the Python GIL. This can lead to
        ///          crashes (undefined behavior) if the Python interpreter is finalizing.
        static void m_fetched_error_deleter(detail::error_fetch_and_normalize *raw_ptr);
    };

    /// Replaces the current Python error indicator with the chosen error, performing a
    /// 'raise from' to indicate that the chosen error was caused by the original error.
    inline void raise_from(PyObject *type, const char *message) {
        // Based on _PyErr_FormatVFromCause:
        // https://github.com/python/cpython/blob/467ab194fc6189d9f7310c89937c51abeac56839/Python/errors.c#L405
        // See https://github.com/pybind/pybind11/pull/2112 for details.
        PyObject *exc = nullptr, *val = nullptr, *val2 = nullptr, *tb = nullptr;

        assert(PyErr_Occurred());
        PyErr_Fetch(&exc, &val, &tb);
        PyErr_NormalizeException(&exc, &val, &tb);
        if (tb != nullptr) {
            PyException_SetTraceback(val, tb);
            Py_DECREF(tb);
        }
        Py_DECREF(exc);
        assert(!PyErr_Occurred());

        PyErr_SetString(type, message);

        PyErr_Fetch(&exc, &val2, &tb);
        PyErr_NormalizeException(&exc, &val2, &tb);
        Py_INCREF(val);
        PyException_SetCause(val2, val);
        PyException_SetContext(val2, val);
        PyErr_Restore(exc, val2, tb);
    }

    /// Sets the current Python error indicator with the chosen error, performing a 'raise from'
    /// from the error contained in error_already_set to indicate that the chosen error was
    /// caused by the original error.
    inline void raise_from(error_already_set &err, PyObject *type, const char *message) {
        err.restore();
        raise_from(type, message);
    }

    /** \defgroup python_builtins const_name
        Unless stated otherwise, the following C++ functions behave the same
        as their Python counterparts.
     */

    /** \ingroup python_builtins
        \rst
        Return true if ``obj`` is an instance of ``T``. Type ``T`` must be a subclass of
        `object` or a class which was exposed to Python as ``py::class_<T>``.
    \endrst */
    template <typename T, detail::enable_if_t<std::is_base_of<object, T>::value, int> = 0>
    bool isinstance(handle obj) {
        return T::check_(obj);
    }

    template <typename T, detail::enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
    bool isinstance(handle obj) {
        return detail::isinstance_generic(obj, typeid(T));
    }

    template <>
    inline bool isinstance<handle>(handle) = delete;
    template <>
    inline bool isinstance<object>(handle obj) {
        return obj.ptr() != nullptr;
    }

    /// \ingroup python_builtins
    /// Return true if ``obj`` is an instance of the ``type``.
    inline bool isinstance(handle obj, handle type) {
        const auto result = PyObject_IsInstance(obj.ptr(), type.ptr());
        if (result == -1) {
            throw error_already_set();
        }
        return result != 0;
    }

    /// \addtogroup python_builtins
    /// @{
    inline bool hasattr(handle obj, handle name) {
        return PyObject_HasAttr(obj.ptr(), name.ptr()) == 1;
    }

    inline bool hasattr(handle obj, const char *name) {
        return PyObject_HasAttrString(obj.ptr(), name) == 1;
    }

    inline void delattr(handle obj, handle name) {
        if (PyObject_DelAttr(obj.ptr(), name.ptr()) != 0) {
            throw error_already_set();
        }
    }

    inline void delattr(handle obj, const char *name) {
        if (PyObject_DelAttrString(obj.ptr(), name) != 0) {
            throw error_already_set();
        }
    }

    inline object getattr(handle obj, handle name) {
        PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr());
        if (!result) {
            throw error_already_set();
        }
        return reinterpret_steal<object>(result);
    }

    inline object getattr(handle obj, const char *name) {
        PyObject *result = PyObject_GetAttrString(obj.ptr(), name);
        if (!result) {
            throw error_already_set();
        }
        return reinterpret_steal<object>(result);
    }

    inline object getattr(handle obj, handle name, handle default_) {
        if (PyObject *result = PyObject_GetAttr(obj.ptr(), name.ptr())) {
            return reinterpret_steal<object>(result);
        }
        PyErr_Clear();
        return reinterpret_borrow<object>(default_);
    }

    inline object getattr(handle obj, const char *name, handle default_) {
        if (PyObject *result = PyObject_GetAttrString(obj.ptr(), name)) {
            return reinterpret_steal<object>(result);
        }
        PyErr_Clear();
        return reinterpret_borrow<object>(default_);
    }

    inline void setattr(handle obj, handle name, handle value) {
        if (PyObject_SetAttr(obj.ptr(), name.ptr(), value.ptr()) != 0) {
            throw error_already_set();
        }
    }

    inline void setattr(handle obj, const char *name, handle value) {
        if (PyObject_SetAttrString(obj.ptr(), name, value.ptr()) != 0) {
            throw error_already_set();
        }
    }

    inline ssize_t hash(handle obj) {
        auto h = PyObject_Hash(obj.ptr());
        if (h == -1) {
            throw error_already_set();
        }
        return h;
    }

    /// @} python_builtins

    PYBIND11_NAMESPACE_BEGIN(detail)
    inline handle get_function(handle value) {
        if (value) {
            if (PyInstanceMethod_Check(value.ptr())) {
                value = PyInstanceMethod_GET_FUNCTION(value.ptr());
            } else if (PyMethod_Check(value.ptr())) {
                value = PyMethod_GET_FUNCTION(value.ptr());
            }
        }
        return value;
    }

    // Reimplementation of python's dict helper functions to ensure that exceptions
    // aren't swallowed (see #2862)

    // copied from cpython _PyDict_GetItemStringWithError
    inline PyObject *dict_getitemstring(PyObject *v, const char *key) {
        PyObject *kv = nullptr, *rv = nullptr;
        kv = PyUnicode_FromString(key);
        if (kv == nullptr) {
            throw error_already_set();
        }

        rv = PyDict_GetItemWithError(v, kv);
        Py_DECREF(kv);
        if (rv == nullptr && PyErr_Occurred()) {
            throw error_already_set();
        }
        return rv;
    }

    inline PyObject *dict_getitem(PyObject *v, PyObject *key) {
        PyObject *rv = PyDict_GetItemWithError(v, key);
        if (rv == nullptr && PyErr_Occurred()) {
            throw error_already_set();
        }
        return rv;
    }

    // Helper aliases/functions to support implicit casting of values given to python
    // accessors/methods. When given a pyobject, this simply returns the pyobject as-is; for other C++
    // type, the value goes through pybind11::cast(obj) to convert it to an `object`.
    template <typename T, enable_if_t<is_pyobject<T>::value, int> = 0>
    auto object_or_cast(T &&o) -> decltype(std::forward<T>(o)) {
        return std::forward<T>(o);
    }
    // The following casting version is implemented in cast.h:
    template <typename T, enable_if_t<!is_pyobject<T>::value, int> = 0>
    object object_or_cast(T &&o);
    // Match a PyObject*, which we want to convert directly to handle via its converting constructor
    inline handle object_or_cast(PyObject *ptr) { return ptr; }

    PYBIND11_WARNING_PUSH
    PYBIND11_WARNING_DISABLE_MSVC(4522) // warning C4522: multiple assignment operators specified
    template <typename Policy>
    class accessor : public object_api<accessor<Policy>> {
        using key_type = typename Policy::key_type;

    public:
        accessor(handle obj, key_type key) : obj(obj), key(std::move(key)) {}
        accessor(const accessor &) = default;
        accessor(accessor &&) noexcept = default;

        // accessor overload required to override default assignment operator (templates are not
        // allowed to replace default compiler-generated assignments).
        void operator=(const accessor &a) && { std::move(*this).operator=(handle(a)); }
        void operator=(const accessor &a) & { operator=(handle(a)); }

        template <typename T>
        void operator=(T &&value) && {
            Policy::set(obj, key, object_or_cast(std::forward<T>(value)));
        }
        template <typename T>
        void operator=(T &&value) & {
            get_cache() = ensure_object(object_or_cast(std::forward<T>(value)));
        }

        template <typename T = Policy>
        PYBIND11_DEPRECATED(
            "Use of obj.attr(...) as bool is deprecated in favor of pybind11::hasattr(obj, ...)")
        explicit
        operator enable_if_t<std::is_same<T, accessor_policies::str_attr>::value
                                 || std::is_same<T, accessor_policies::obj_attr>::value,
                             bool>() const {
            return hasattr(obj, key);
        }
        template <typename T = Policy>
        PYBIND11_DEPRECATED("Use of obj[key] as bool is deprecated in favor of obj.contains(key)")
        explicit
        operator enable_if_t<std::is_same<T, accessor_policies::generic_item>::value, bool>() const {
            return obj.contains(key);
        }

        // NOLINTNEXTLINE(google-explicit-constructor)
        operator object() const { return get_cache(); }
        PyObject *ptr() const { return get_cache().ptr(); }
        template <typename T>
        T cast() const {
            return get_cache().template cast<T>();
        }

    private:
        static object ensure_object(object &&o) { return std::move(o); }
        static object ensure_object(handle h) { return reinterpret_borrow<object>(h); }

        object &get_cache() const {
            if (!cache) {
                cache = Policy::get(obj, key);
            }
            return cache;
        }

    private:
        handle obj;
        key_type key;
        mutable object cache;
    };
    PYBIND11_WARNING_POP

    PYBIND11_NAMESPACE_BEGIN(accessor_policies)
    struct obj_attr {
        using key_type = object;
        static object get(handle obj, handle key) { return getattr(obj, key); }
        static void set(handle obj, handle key, handle val) { setattr(obj, key, val); }
    };

    struct str_attr {
        using key_type = const char *;
        static object get(handle obj, const char *key) { return getattr(obj, key); }
        static void set(handle obj, const char *key, handle val) { setattr(obj, key, val); }
    };

    struct generic_item {
        using key_type = object;

        static object get(handle obj, handle key) {
            PyObject *result = PyObject_GetItem(obj.ptr(), key.ptr());
            if (!result) {
                throw error_already_set();
            }
            return reinterpret_steal<object>(result);
        }

        static void set(handle obj, handle key, handle val) {
            if (PyObject_SetItem(obj.ptr(), key.ptr(), val.ptr()) != 0) {
                throw error_already_set();
            }
        }
    };

    struct sequence_item {
        using key_type = size_t;

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static object get(handle obj, const IdxType &index) {
            PyObject *result = PySequence_GetItem(obj.ptr(), ssize_t_cast(index));
            if (!result) {
                throw error_already_set();
            }
            return reinterpret_steal<object>(result);
        }

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static void set(handle obj, const IdxType &index, handle val) {
            // PySequence_SetItem does not steal a reference to 'val'
            if (PySequence_SetItem(obj.ptr(), ssize_t_cast(index), val.ptr()) != 0) {
                throw error_already_set();
            }
        }
    };

    struct list_item {
        using key_type = size_t;

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static object get(handle obj, const IdxType &index) {
            PyObject *result = PyList_GetItem(obj.ptr(), ssize_t_cast(index));
            if (!result) {
                throw error_already_set();
            }
            return reinterpret_borrow<object>(result);
        }

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static void set(handle obj, const IdxType &index, handle val) {
            // PyList_SetItem steals a reference to 'val'
            if (PyList_SetItem(obj.ptr(), ssize_t_cast(index), val.inc_ref().ptr()) != 0) {
                throw error_already_set();
            }
        }
    };

    struct tuple_item {
        using key_type = size_t;

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static object get(handle obj, const IdxType &index) {
            PyObject *result = PyTuple_GetItem(obj.ptr(), ssize_t_cast(index));
            if (!result) {
                throw error_already_set();
            }
            return reinterpret_borrow<object>(result);
        }

        template <typename IdxType, detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        static void set(handle obj, const IdxType &index, handle val) {
            // PyTuple_SetItem steals a reference to 'val'
            if (PyTuple_SetItem(obj.ptr(), ssize_t_cast(index), val.inc_ref().ptr()) != 0) {
                throw error_already_set();
            }
        }
    };
    PYBIND11_NAMESPACE_END(accessor_policies)

    /// STL iterator template used for tuple, list, sequence and dict
    template <typename Policy>
    class generic_iterator : public Policy {
        using It = generic_iterator;

    public:
        using difference_type = ssize_t;
        using iterator_category = typename Policy::iterator_category;
        using value_type = typename Policy::value_type;
        using reference = typename Policy::reference;
        using pointer = typename Policy::pointer;

        generic_iterator() = default;
        generic_iterator(handle seq, ssize_t index) : Policy(seq, index) {}

        // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
        reference operator*() const { return Policy::dereference(); }
        // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
        reference operator[](difference_type n) const { return *(*this + n); }
        pointer operator->() const { return **this; }

        It &operator++() {
            Policy::increment();
            return *this;
        }
        It operator++(int) {
            auto copy = *this;
            Policy::increment();
            return copy;
        }
        It &operator--() {
            Policy::decrement();
            return *this;
        }
        It operator--(int) {
            auto copy = *this;
            Policy::decrement();
            return copy;
        }
        It &operator+=(difference_type n) {
            Policy::advance(n);
            return *this;
        }
        It &operator-=(difference_type n) {
            Policy::advance(-n);
            return *this;
        }

        friend It operator+(const It &a, difference_type n) {
            auto copy = a;
            return copy += n;
        }
        friend It operator+(difference_type n, const It &b) { return b + n; }
        friend It operator-(const It &a, difference_type n) {
            auto copy = a;
            return copy -= n;
        }
        friend difference_type operator-(const It &a, const It &b) { return a.distance_to(b); }

        friend bool operator==(const It &a, const It &b) { return a.equal(b); }
        friend bool operator!=(const It &a, const It &b) { return !(a == b); }
        friend bool operator<(const It &a, const It &b) { return b - a > 0; }
        friend bool operator>(const It &a, const It &b) { return b < a; }
        friend bool operator>=(const It &a, const It &b) { return !(a < b); }
        friend bool operator<=(const It &a, const It &b) { return !(a > b); }
    };

    PYBIND11_NAMESPACE_BEGIN(iterator_policies)
    /// Quick proxy class needed to implement ``operator->`` for iterators which can't return pointers
    template <typename T>
    struct arrow_proxy {
        T value;

        // NOLINTNEXTLINE(google-explicit-constructor)
        arrow_proxy(T &&value) noexcept : value(std::move(value)) {}
        T *operator->() const { return &value; }
    };

    /// Lightweight iterator policy using just a simple pointer: see ``PySequence_Fast_ITEMS``
    class sequence_fast_readonly {
    protected:
        using iterator_category = std::random_access_iterator_tag;
        using value_type = handle;
        using reference = const handle; // PR #3263
        using pointer = arrow_proxy<const handle>;

        sequence_fast_readonly(handle obj, ssize_t n) : ptr(PySequence_Fast_ITEMS(obj.ptr()) + n) {}

        // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
        reference dereference() const { return *ptr; }
        void increment() { ++ptr; }
        void decrement() { --ptr; }
        void advance(ssize_t n) { ptr += n; }
        bool equal(const sequence_fast_readonly &b) const { return ptr == b.ptr; }
        ssize_t distance_to(const sequence_fast_readonly &b) const { return ptr - b.ptr; }

    private:
        PyObject **ptr;
    };

    /// Full read and write access using the sequence protocol: see ``detail::sequence_accessor``
    class sequence_slow_readwrite {
    protected:
        using iterator_category = std::random_access_iterator_tag;
        using value_type = object;
        using reference = sequence_accessor;
        using pointer = arrow_proxy<const sequence_accessor>;

        sequence_slow_readwrite(handle obj, ssize_t index) : obj(obj), index(index) {}

        reference dereference() const { return {obj, static_cast<size_t>(index)}; }
        void increment() { ++index; }
        void decrement() { --index; }
        void advance(ssize_t n) { index += n; }
        bool equal(const sequence_slow_readwrite &b) const { return index == b.index; }
        ssize_t distance_to(const sequence_slow_readwrite &b) const { return index - b.index; }

    private:
        handle obj;
        ssize_t index;
    };

    /// Python's dictionary protocol permits this to be a forward iterator
    class dict_readonly {
    protected:
        using iterator_category = std::forward_iterator_tag;
        using value_type = std::pair<handle, handle>;
        using reference = const value_type; // PR #3263
        using pointer = arrow_proxy<const value_type>;

        dict_readonly() = default;
        dict_readonly(handle obj, ssize_t pos) : obj(obj), pos(pos) { increment(); }

        // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
        reference dereference() const { return {key, value}; }
        void increment() {
            if (PyDict_Next(obj.ptr(), &pos, &key, &value) == 0) {
                pos = -1;
            }
        }
        bool equal(const dict_readonly &b) const { return pos == b.pos; }

    private:
        handle obj;
        PyObject *key = nullptr, *value = nullptr;
        ssize_t pos = -1;
    };
    PYBIND11_NAMESPACE_END(iterator_policies)

    #if !defined(PYPY_VERSION)
    using tuple_iterator = generic_iterator<iterator_policies::sequence_fast_readonly>;
    using list_iterator = generic_iterator<iterator_policies::sequence_fast_readonly>;
    #else
    using tuple_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
    using list_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
    #endif

    using sequence_iterator = generic_iterator<iterator_policies::sequence_slow_readwrite>;
    using dict_iterator = generic_iterator<iterator_policies::dict_readonly>;

    inline bool PyIterable_Check(PyObject *obj) {
        PyObject *iter = PyObject_GetIter(obj);
        if (iter) {
            Py_DECREF(iter);
            return true;
        }
        PyErr_Clear();
        return false;
    }

    inline bool PyNone_Check(PyObject *o) { return o == Py_None; }
    inline bool PyEllipsis_Check(PyObject *o) { return o == Py_Ellipsis; }

    #ifdef PYBIND11_STR_LEGACY_PERMISSIVE
    inline bool PyUnicode_Check_Permissive(PyObject *o) {
        return PyUnicode_Check(o) || PYBIND11_BYTES_CHECK(o);
    }
    #    define PYBIND11_STR_CHECK_FUN detail::PyUnicode_Check_Permissive
    #else
    #    define PYBIND11_STR_CHECK_FUN PyUnicode_Check
    #endif

    inline bool PyStaticMethod_Check(PyObject *o) { return o->ob_type == &PyStaticMethod_Type; }

    class kwargs_proxy : public handle {
    public:
        explicit kwargs_proxy(handle h) : handle(h) {}
    };

    class args_proxy : public handle {
    public:
        explicit args_proxy(handle h) : handle(h) {}
        kwargs_proxy operator*() const { return kwargs_proxy(*this); }
    };

    /// Python argument categories (using PEP 448 terms)
    template <typename T>
    using is_keyword = std::is_base_of<arg, T>;
    template <typename T>
    using is_s_unpacking = std::is_same<args_proxy, T>; // * unpacking
    template <typename T>
    using is_ds_unpacking = std::is_same<kwargs_proxy, T>; // ** unpacking
    template <typename T>
    using is_positional = satisfies_none_of<T, is_keyword, is_s_unpacking, is_ds_unpacking>;
    template <typename T>
    using is_keyword_or_ds = satisfies_any_of<T, is_keyword, is_ds_unpacking>;

    // Call argument collector forward declarations
    template <return_value_policy policy = return_value_policy::automatic_reference>
    class simple_collector;
    template <return_value_policy policy = return_value_policy::automatic_reference>
    class unpacking_collector;

    PYBIND11_NAMESPACE_END(detail)

    // TODO: After the deprecated constructors are removed, this macro can be simplified by
    //       inheriting ctors: `using Parent::Parent`. It's not an option right now because
    //       the `using` statement triggers the parent deprecation warning even if the ctor
    //       isn't even used.
    #define PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                            \
    public:                                                                                           \
        PYBIND11_DEPRECATED("Use reinterpret_borrow<" #Name ">() or reinterpret_steal<" #Name ">()")  \
        Name(handle h, bool is_borrowed)                                                              \
            : Parent(is_borrowed ? Parent(h, borrowed_t{}) : Parent(h, stolen_t{})) {}                \
        Name(handle h, borrowed_t) : Parent(h, borrowed_t{}) {}                                       \
        Name(handle h, stolen_t) : Parent(h, stolen_t{}) {}                                           \
        PYBIND11_DEPRECATED("Use py::isinstance<py::python_type>(obj) instead")                       \
        bool check() const { return m_ptr != nullptr && (CheckFun(m_ptr) != 0); }                     \
        static bool check_(handle h) { return h.ptr() != nullptr && CheckFun(h.ptr()); }              \
        template <typename Policy_> /* NOLINTNEXTLINE(google-explicit-constructor) */                 \
        Name(const ::pybind11::detail::accessor<Policy_> &a) : Name(object(a)) {}

    #define PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                   \
        PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
        /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
        /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
        Name(const object &o)                                                                         \
            : Parent(check_(o) ? o.inc_ref().ptr() : ConvertFun(o.ptr()), stolen_t{}) {               \
            if (!m_ptr)                                                                               \
                throw ::pybind11::error_already_set();                                                \
        }                                                                                             \
        /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
        Name(object &&o) : Parent(check_(o) ? o.release().ptr() : ConvertFun(o.ptr()), stolen_t{}) {  \
            if (!m_ptr)                                                                               \
                throw ::pybind11::error_already_set();                                                \
        }

    #define PYBIND11_OBJECT_CVT_DEFAULT(Name, Parent, CheckFun, ConvertFun)                           \
        PYBIND11_OBJECT_CVT(Name, Parent, CheckFun, ConvertFun)                                       \
        Name() = default;

    #define PYBIND11_OBJECT_CHECK_FAILED(Name, o_ptr)                                                 \
        ::pybind11::type_error("Object of type '"                                                     \
                               + ::pybind11::detail::get_fully_qualified_tp_name(Py_TYPE(o_ptr))      \
                               + "' is not an instance of '" #Name "'")

    #define PYBIND11_OBJECT(Name, Parent, CheckFun)                                                   \
        PYBIND11_OBJECT_COMMON(Name, Parent, CheckFun)                                                \
        /* This is deliberately not 'explicit' to allow implicit conversion from object: */           \
        /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
        Name(const object &o) : Parent(o) {                                                           \
            if (m_ptr && !check_(m_ptr))                                                              \
                throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
        }                                                                                             \
        /* NOLINTNEXTLINE(google-explicit-constructor) */                                             \
        Name(object &&o) : Parent(std::move(o)) {                                                     \
            if (m_ptr && !check_(m_ptr))                                                              \
                throw PYBIND11_OBJECT_CHECK_FAILED(Name, m_ptr);                                      \
        }

    #define PYBIND11_OBJECT_DEFAULT(Name, Parent, CheckFun)                                           \
        PYBIND11_OBJECT(Name, Parent, CheckFun)                                                       \
        Name() = default;

    /// \addtogroup pytypes
    /// @{

    /** \rst
        Wraps a Python iterator so that it can also be used as a C++ input iterator

        Caveat: copying an iterator does not (and cannot) clone the internal
        state of the Python iterable. This also applies to the post-increment
        operator. This iterator should only be used to retrieve the current
        value using ``operator*()``.
    \endrst */
    class iterator : public object {
    public:
        using iterator_category = std::input_iterator_tag;
        using difference_type = ssize_t;
        using value_type = handle;
        using reference = const handle; // PR #3263
        using pointer = const handle *;

        PYBIND11_OBJECT_DEFAULT(iterator, object, PyIter_Check)

        iterator &operator++() {
            advance();
            return *this;
        }

        iterator operator++(int) {
            auto rv = *this;
            advance();
            return rv;
        }

        // NOLINTNEXTLINE(readability-const-return-type) // PR #3263
        reference operator*() const {
            if (m_ptr && !value.ptr()) {
                auto &self = const_cast<iterator &>(*this);
                self.advance();
            }
            return value;
        }

        pointer operator->() const {
            operator*();
            return &value;
        }

        /** \rst
             The value which marks the end of the iteration. ``it == iterator::sentinel()``
             is equivalent to catching ``StopIteration`` in Python.

             .. code-block:: cpp

                 void foo(py::iterator it) {
                     while (it != py::iterator::sentinel()) {
                        // use `*it`
                        ++it;
                     }
                 }
        \endrst */
        static iterator sentinel() { return {}; }

        friend bool operator==(const iterator &a, const iterator &b) { return a->ptr() == b->ptr(); }
        friend bool operator!=(const iterator &a, const iterator &b) { return a->ptr() != b->ptr(); }

    private:
        void advance() {
            value = reinterpret_steal<object>(PyIter_Next(m_ptr));
            if (value.ptr() == nullptr && PyErr_Occurred()) {
                throw error_already_set();
            }
        }

    private:
        object value = {};
    };

    class type : public object {
    public:
        PYBIND11_OBJECT(type, object, PyType_Check)

        /// Return a type handle from a handle or an object
        static handle handle_of(handle h) { return handle((PyObject *) Py_TYPE(h.ptr())); }

        /// Return a type object from a handle or an object
        static type of(handle h) { return type(type::handle_of(h), borrowed_t{}); }

        // Defined in pybind11/cast.h
        /// Convert C++ type to handle if previously registered. Does not convert
        /// standard types, like int, float. etc. yet.
        /// See https://github.com/pybind/pybind11/issues/2486
        template <typename T>
        static handle handle_of();

        /// Convert C++ type to type if previously registered. Does not convert
        /// standard types, like int, float. etc. yet.
        /// See https://github.com/pybind/pybind11/issues/2486
        template <typename T>
        static type of() {
            return type(type::handle_of<T>(), borrowed_t{});
        }
    };

    class iterable : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(iterable, object, detail::PyIterable_Check)
    };

    class bytes;

    class str : public object {
    public:
        PYBIND11_OBJECT_CVT(str, object, PYBIND11_STR_CHECK_FUN, raw_str)

        template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
        str(const char *c, const SzType &n)
            : object(PyUnicode_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
            if (!m_ptr) {
                if (PyErr_Occurred()) {
                    throw error_already_set();
                }
                pybind11_fail("Could not allocate string object!");
            }
        }

        // 'explicit' is explicitly omitted from the following constructors to allow implicit
        // conversion to py::str from C++ string-like objects
        // NOLINTNEXTLINE(google-explicit-constructor)
        str(const char *c = "") : object(PyUnicode_FromString(c), stolen_t{}) {
            if (!m_ptr) {
                if (PyErr_Occurred()) {
                    throw error_already_set();
                }
                pybind11_fail("Could not allocate string object!");
            }
        }

        // NOLINTNEXTLINE(google-explicit-constructor)
        str(const std::string &s) : str(s.data(), s.size()) {}

    #ifdef PYBIND11_HAS_STRING_VIEW
        // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
        template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        str(T s) : str(s.data(), s.size()) {}

    #    ifdef PYBIND11_HAS_U8STRING
        // reinterpret_cast here is safe (C++20 guarantees char8_t has the same size/alignment as char)
        // NOLINTNEXTLINE(google-explicit-constructor)
        str(std::u8string_view s) : str(reinterpret_cast<const char *>(s.data()), s.size()) {}
    #    endif

    #endif

        explicit str(const bytes &b);

        /** \rst
            Return a string representation of the object. This is analogous to
            the ``str()`` function in Python.
        \endrst */
        explicit str(handle h) : object(raw_str(h.ptr()), stolen_t{}) {
            if (!m_ptr) {
                throw error_already_set();
            }
        }

        // NOLINTNEXTLINE(google-explicit-constructor)
        operator std::string() const {
            object temp = *this;
            if (PyUnicode_Check(m_ptr)) {
                temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(m_ptr));
                if (!temp) {
                    throw error_already_set();
                }
            }
            char *buffer = nullptr;
            ssize_t length = 0;
            if (PyBytes_AsStringAndSize(temp.ptr(), &buffer, &length) != 0) {
                throw error_already_set();
            }
            return std::string(buffer, (size_t) length);
        }

        template <typename... Args>
        str format(Args &&...args) const {
            return attr("format")(std::forward<Args>(args)...);
        }

    private:
        /// Return string representation -- always returns a new reference, even if already a str
        static PyObject *raw_str(PyObject *op) {
            PyObject *str_value = PyObject_Str(op);
            return str_value;
        }
    };
    /// @} pytypes

    inline namespace literals {
    /** \rst
        String literal version of `str`
     \endrst */
    inline str
    #if !defined(__clang__) && defined(__GNUC__) && __GNUC__ < 5
    operator"" _s // gcc 4.8.5 insists on having a space (hard error).
    #else
    operator""_s // clang 17 generates a deprecation warning if there is a space.
    #endif
        (const char *s, size_t size) {
        return {s, size};
    }
    } // namespace literals

    /// \addtogroup pytypes
    /// @{
    class bytes : public object {
    public:
        PYBIND11_OBJECT(bytes, object, PYBIND11_BYTES_CHECK)

        // Allow implicit conversion:
        // NOLINTNEXTLINE(google-explicit-constructor)
        bytes(const char *c = "") : object(PYBIND11_BYTES_FROM_STRING(c), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate bytes object!");
            }
        }

        template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
        bytes(const char *c, const SzType &n)
            : object(PYBIND11_BYTES_FROM_STRING_AND_SIZE(c, ssize_t_cast(n)), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate bytes object!");
            }
        }

        // Allow implicit conversion:
        // NOLINTNEXTLINE(google-explicit-constructor)
        bytes(const std::string &s) : bytes(s.data(), s.size()) {}

        explicit bytes(const pybind11::str &s);

        // NOLINTNEXTLINE(google-explicit-constructor)
        operator std::string() const { return string_op<std::string>(); }

    #ifdef PYBIND11_HAS_STRING_VIEW
        // enable_if is needed to avoid "ambiguous conversion" errors (see PR #3521).
        template <typename T, detail::enable_if_t<std::is_same<T, std::string_view>::value, int> = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        bytes(T s) : bytes(s.data(), s.size()) {}

        // Obtain a string view that views the current `bytes` buffer value.  Note that this is only
        // valid so long as the `bytes` instance remains alive and so generally should not outlive the
        // lifetime of the `bytes` instance.
        // NOLINTNEXTLINE(google-explicit-constructor)
        operator std::string_view() const { return string_op<std::string_view>(); }
    #endif
    private:
        template <typename T>
        T string_op() const {
            char *buffer = nullptr;
            ssize_t length = 0;
            if (PyBytes_AsStringAndSize(m_ptr, &buffer, &length) != 0) {
                throw error_already_set();
            }
            return {buffer, static_cast<size_t>(length)};
        }
    };
    // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
    // are included in the doxygen group; close here and reopen after as a workaround
    /// @} pytypes

    inline bytes::bytes(const pybind11::str &s) {
        object temp = s;
        if (PyUnicode_Check(s.ptr())) {
            temp = reinterpret_steal<object>(PyUnicode_AsUTF8String(s.ptr()));
            if (!temp) {
                throw error_already_set();
            }
        }
        char *buffer = nullptr;
        ssize_t length = 0;
        if (PyBytes_AsStringAndSize(temp.ptr(), &buffer, &length) != 0) {
            throw error_already_set();
        }
        auto obj = reinterpret_steal<object>(PYBIND11_BYTES_FROM_STRING_AND_SIZE(buffer, length));
        if (!obj) {
            pybind11_fail("Could not allocate bytes object!");
        }
        m_ptr = obj.release().ptr();
    }

    inline str::str(const bytes &b) {
        char *buffer = nullptr;
        ssize_t length = 0;
        if (PyBytes_AsStringAndSize(b.ptr(), &buffer, &length) != 0) {
            throw error_already_set();
        }
        auto obj = reinterpret_steal<object>(PyUnicode_FromStringAndSize(buffer, length));
        if (!obj) {
            if (PyErr_Occurred()) {
                throw error_already_set();
            }
            pybind11_fail("Could not allocate string object!");
        }
        m_ptr = obj.release().ptr();
    }

    /// \addtogroup pytypes
    /// @{
    class bytearray : public object {
    public:
        PYBIND11_OBJECT_CVT(bytearray, object, PyByteArray_Check, PyByteArray_FromObject)

        template <typename SzType, detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
        bytearray(const char *c, const SzType &n)
            : object(PyByteArray_FromStringAndSize(c, ssize_t_cast(n)), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate bytearray object!");
            }
        }

        bytearray() : bytearray("", 0) {}

        explicit bytearray(const std::string &s) : bytearray(s.data(), s.size()) {}

        size_t size() const { return static_cast<size_t>(PyByteArray_Size(m_ptr)); }

        explicit operator std::string() const {
            char *buffer = PyByteArray_AS_STRING(m_ptr);
            ssize_t size = PyByteArray_GET_SIZE(m_ptr);
            return std::string(buffer, static_cast<size_t>(size));
        }
    };
    // Note: breathe >= 4.17.0 will fail to build docs if the below two constructors
    // are included in the doxygen group; close here and reopen after as a workaround
    /// @} pytypes

    /// \addtogroup pytypes
    /// @{
    class none : public object {
    public:
        PYBIND11_OBJECT(none, object, detail::PyNone_Check)
        none() : object(Py_None, borrowed_t{}) {}
    };

    class ellipsis : public object {
    public:
        PYBIND11_OBJECT(ellipsis, object, detail::PyEllipsis_Check)
        ellipsis() : object(Py_Ellipsis, borrowed_t{}) {}
    };

    class bool_ : public object {
    public:
        PYBIND11_OBJECT_CVT(bool_, object, PyBool_Check, raw_bool)
        bool_() : object(Py_False, borrowed_t{}) {}
        // Allow implicit conversion from and to `bool`:
        // NOLINTNEXTLINE(google-explicit-constructor)
        bool_(bool value) : object(value ? Py_True : Py_False, borrowed_t{}) {}
        // NOLINTNEXTLINE(google-explicit-constructor)
        operator bool() const { return (m_ptr != nullptr) && PyLong_AsLong(m_ptr) != 0; }

    private:
        /// Return the truth value of an object -- always returns a new reference
        static PyObject *raw_bool(PyObject *op) {
            const auto value = PyObject_IsTrue(op);
            if (value == -1) {
                return nullptr;
            }
            return handle(value != 0 ? Py_True : Py_False).inc_ref().ptr();
        }
    };

    PYBIND11_NAMESPACE_BEGIN(detail)
    // Converts a value to the given unsigned type.  If an error occurs, you get back (Unsigned) -1;
    // otherwise you get back the unsigned long or unsigned long long value cast to (Unsigned).
    // (The distinction is critically important when casting a returned -1 error value to some other
    // unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
    template <typename Unsigned>
    Unsigned as_unsigned(PyObject *o) {
        if (sizeof(Unsigned) <= sizeof(unsigned long)) {
            unsigned long v = PyLong_AsUnsignedLong(o);
            return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
        }
        unsigned long long v = PyLong_AsUnsignedLongLong(o);
        return v == (unsigned long long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
    }
    PYBIND11_NAMESPACE_END(detail)

    class int_ : public object {
    public:
        PYBIND11_OBJECT_CVT(int_, object, PYBIND11_LONG_CHECK, PyNumber_Long)
        int_() : object(PyLong_FromLong(0), stolen_t{}) {}
        // Allow implicit conversion from C++ integral types:
        template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        int_(T value) {
            if (sizeof(T) <= sizeof(long)) {
                if (std::is_signed<T>::value) {
                    m_ptr = PyLong_FromLong((long) value);
                } else {
                    m_ptr = PyLong_FromUnsignedLong((unsigned long) value);
                }
            } else {
                if (std::is_signed<T>::value) {
                    m_ptr = PyLong_FromLongLong((long long) value);
                } else {
                    m_ptr = PyLong_FromUnsignedLongLong((unsigned long long) value);
                }
            }
            if (!m_ptr) {
                pybind11_fail("Could not allocate int object!");
            }
        }

        template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
        // NOLINTNEXTLINE(google-explicit-constructor)
        operator T() const {
            return std::is_unsigned<T>::value  ? detail::as_unsigned<T>(m_ptr)
                   : sizeof(T) <= sizeof(long) ? (T) PyLong_AsLong(m_ptr)
                                               : (T) PYBIND11_LONG_AS_LONGLONG(m_ptr);
        }
    };

    class float_ : public object {
    public:
        PYBIND11_OBJECT_CVT(float_, object, PyFloat_Check, PyNumber_Float)
        // Allow implicit conversion from float/double:
        // NOLINTNEXTLINE(google-explicit-constructor)
        float_(float value) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate float object!");
            }
        }
        // NOLINTNEXTLINE(google-explicit-constructor)
        float_(double value = .0) : object(PyFloat_FromDouble((double) value), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate float object!");
            }
        }
        // NOLINTNEXTLINE(google-explicit-constructor)
        operator float() const { return (float) PyFloat_AsDouble(m_ptr); }
        // NOLINTNEXTLINE(google-explicit-constructor)
        operator double() const { return (double) PyFloat_AsDouble(m_ptr); }
    };

    class weakref : public object {
    public:
        PYBIND11_OBJECT_CVT_DEFAULT(weakref, object, PyWeakref_Check, raw_weakref)
        explicit weakref(handle obj, handle callback = {})
            : object(PyWeakref_NewRef(obj.ptr(), callback.ptr()), stolen_t{}) {
            if (!m_ptr) {
                if (PyErr_Occurred()) {
                    throw error_already_set();
                }
                pybind11_fail("Could not allocate weak reference!");
            }
        }

    private:
        static PyObject *raw_weakref(PyObject *o) { return PyWeakref_NewRef(o, nullptr); }
    };

    class slice : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(slice, object, PySlice_Check)
        slice(handle start, handle stop, handle step)
            : object(PySlice_New(start.ptr(), stop.ptr(), step.ptr()), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate slice object!");
            }
        }

    #ifdef PYBIND11_HAS_OPTIONAL
        slice(std::optional<ssize_t> start, std::optional<ssize_t> stop, std::optional<ssize_t> step)
            : slice(index_to_object(start), index_to_object(stop), index_to_object(step)) {}
    #else
        slice(ssize_t start_, ssize_t stop_, ssize_t step_)
            : slice(int_(start_), int_(stop_), int_(step_)) {}
    #endif

        bool
        compute(size_t length, size_t *start, size_t *stop, size_t *step, size_t *slicelength) const {
            return PySlice_GetIndicesEx((PYBIND11_SLICE_OBJECT *) m_ptr,
                                        (ssize_t) length,
                                        (ssize_t *) start,
                                        (ssize_t *) stop,
                                        (ssize_t *) step,
                                        (ssize_t *) slicelength)
                   == 0;
        }
        bool compute(
            ssize_t length, ssize_t *start, ssize_t *stop, ssize_t *step, ssize_t *slicelength) const {
            return PySlice_GetIndicesEx(
                       (PYBIND11_SLICE_OBJECT *) m_ptr, length, start, stop, step, slicelength)
                   == 0;
        }

    private:
        template <typename T>
        static object index_to_object(T index) {
            return index ? object(int_(*index)) : object(none());
        }
    };

    class capsule : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(capsule, object, PyCapsule_CheckExact)
        PYBIND11_DEPRECATED("Use reinterpret_borrow<capsule>() or reinterpret_steal<capsule>()")
        capsule(PyObject *ptr, bool is_borrowed)
            : object(is_borrowed ? object(ptr, borrowed_t{}) : object(ptr, stolen_t{})) {}

        explicit capsule(const void *value,
                         const char *name = nullptr,
                         PyCapsule_Destructor destructor = nullptr)
            : object(PyCapsule_New(const_cast<void *>(value), name, destructor), stolen_t{}) {
            if (!m_ptr) {
                throw error_already_set();
            }
        }

        PYBIND11_DEPRECATED("Please use the ctor with value, name, destructor args")
        capsule(const void *value, PyCapsule_Destructor destructor)
            : object(PyCapsule_New(const_cast<void *>(value), nullptr, destructor), stolen_t{}) {
            if (!m_ptr) {
                throw error_already_set();
            }
        }

        /// Capsule name is nullptr.
        capsule(const void *value, void (*destructor)(void *)) {
            initialize_with_void_ptr_destructor(value, nullptr, destructor);
        }

        capsule(const void *value, const char *name, void (*destructor)(void *)) {
            initialize_with_void_ptr_destructor(value, name, destructor);
        }

        explicit capsule(void (*destructor)()) {
            m_ptr = PyCapsule_New(reinterpret_cast<void *>(destructor), nullptr, [](PyObject *o) {
                const char *name = get_name_in_error_scope(o);
                auto destructor = reinterpret_cast<void (*)()>(PyCapsule_GetPointer(o, name));
                if (destructor == nullptr) {
                    throw error_already_set();
                }
                destructor();
            });

            if (!m_ptr) {
                throw error_already_set();
            }
        }

        template <typename T>
        operator T *() const { // NOLINT(google-explicit-constructor)
            return get_pointer<T>();
        }

        /// Get the pointer the capsule holds.
        template <typename T = void>
        T *get_pointer() const {
            const auto *name = this->name();
            T *result = static_cast<T *>(PyCapsule_GetPointer(m_ptr, name));
            if (!result) {
                throw error_already_set();
            }
            return result;
        }

        /// Replaces a capsule's pointer *without* calling the destructor on the existing one.
        void set_pointer(const void *value) {
            if (PyCapsule_SetPointer(m_ptr, const_cast<void *>(value)) != 0) {
                throw error_already_set();
            }
        }

        const char *name() const {
            const char *name = PyCapsule_GetName(m_ptr);
            if ((name == nullptr) && PyErr_Occurred()) {
                throw error_already_set();
            }
            return name;
        }

        /// Replaces a capsule's name *without* calling the destructor on the existing one.
        void set_name(const char *new_name) {
            if (PyCapsule_SetName(m_ptr, new_name) != 0) {
                throw error_already_set();
            }
        }

    private:
        static const char *get_name_in_error_scope(PyObject *o) {
            error_scope error_guard;

            const char *name = PyCapsule_GetName(o);
            if ((name == nullptr) && PyErr_Occurred()) {
                // write out and consume error raised by call to PyCapsule_GetName
                PyErr_WriteUnraisable(o);
            }

            return name;
        }

        void initialize_with_void_ptr_destructor(const void *value,
                                                 const char *name,
                                                 void (*destructor)(void *)) {
            m_ptr = PyCapsule_New(const_cast<void *>(value), name, [](PyObject *o) {
                // guard if destructor called while err indicator is set
                error_scope error_guard;
                auto destructor = reinterpret_cast<void (*)(void *)>(PyCapsule_GetContext(o));
                if (destructor == nullptr && PyErr_Occurred()) {
                    throw error_already_set();
                }
                const char *name = get_name_in_error_scope(o);
                void *ptr = PyCapsule_GetPointer(o, name);
                if (ptr == nullptr) {
                    throw error_already_set();
                }

                if (destructor != nullptr) {
                    destructor(ptr);
                }
            });

            if (!m_ptr || PyCapsule_SetContext(m_ptr, reinterpret_cast<void *>(destructor)) != 0) {
                throw error_already_set();
            }
        }
    };

    class tuple : public object {
    public:
        PYBIND11_OBJECT_CVT(tuple, object, PyTuple_Check, PySequence_Tuple)
        template <typename SzType = ssize_t,
                  detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
        // Some compilers generate link errors when using `const SzType &` here:
        explicit tuple(SzType size = 0) : object(PyTuple_New(ssize_t_cast(size)), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate tuple object!");
            }
        }
        size_t size() const { return (size_t) PyTuple_Size(m_ptr); }
        bool empty() const { return size() == 0; }
        detail::tuple_accessor operator[](size_t index) const { return {*this, index}; }
        template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
        detail::item_accessor operator[](T &&o) const {
            return object::operator[](std::forward<T>(o));
        }
        detail::tuple_iterator begin() const { return {*this, 0}; }
        detail::tuple_iterator end() const { return {*this, PyTuple_GET_SIZE(m_ptr)}; }
    };

    // We need to put this into a separate function because the Intel compiler
    // fails to compile enable_if_t<all_of<is_keyword_or_ds<Args>...>::value> part below
    // (tested with ICC 2021.1 Beta 20200827).
    template <typename... Args>
    constexpr bool args_are_all_keyword_or_ds() {
        return detail::all_of<detail::is_keyword_or_ds<Args>...>::value;
    }

    class dict : public object {
    public:
        PYBIND11_OBJECT_CVT(dict, object, PyDict_Check, raw_dict)
        dict() : object(PyDict_New(), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate dict object!");
            }
        }
        template <typename... Args,
                  typename = detail::enable_if_t<args_are_all_keyword_or_ds<Args...>()>,
                  // MSVC workaround: it can't compile an out-of-line definition, so defer the
                  // collector
                  typename collector = detail::deferred_t<detail::unpacking_collector<>, Args...>>
        explicit dict(Args &&...args) : dict(collector(std::forward<Args>(args)...).kwargs()) {}

        size_t size() const { return (size_t) PyDict_Size(m_ptr); }
        bool empty() const { return size() == 0; }
        detail::dict_iterator begin() const { return {*this, 0}; }
        detail::dict_iterator end() const { return {}; }
        void clear() /* py-non-const */ { PyDict_Clear(ptr()); }
        template <typename T>
        bool contains(T &&key) const {
            auto result = PyDict_Contains(m_ptr, detail::object_or_cast(std::forward<T>(key)).ptr());
            if (result == -1) {
                throw error_already_set();
            }
            return result == 1;
        }

    private:
        /// Call the `dict` Python type -- always returns a new reference
        static PyObject *raw_dict(PyObject *op) {
            if (PyDict_Check(op)) {
                return handle(op).inc_ref().ptr();
            }
            return PyObject_CallFunctionObjArgs((PyObject *) &PyDict_Type, op, nullptr);
        }
    };

    class sequence : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(sequence, object, PySequence_Check)
        size_t size() const {
            ssize_t result = PySequence_Size(m_ptr);
            if (result == -1) {
                throw error_already_set();
            }
            return (size_t) result;
        }
        bool empty() const { return size() == 0; }
        detail::sequence_accessor operator[](size_t index) const { return {*this, index}; }
        template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
        detail::item_accessor operator[](T &&o) const {
            return object::operator[](std::forward<T>(o));
        }
        detail::sequence_iterator begin() const { return {*this, 0}; }
        detail::sequence_iterator end() const { return {*this, PySequence_Size(m_ptr)}; }
    };

    class list : public object {
    public:
        PYBIND11_OBJECT_CVT(list, object, PyList_Check, PySequence_List)
        template <typename SzType = ssize_t,
                  detail::enable_if_t<std::is_integral<SzType>::value, int> = 0>
        // Some compilers generate link errors when using `const SzType &` here:
        explicit list(SzType size = 0) : object(PyList_New(ssize_t_cast(size)), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate list object!");
            }
        }
        size_t size() const { return (size_t) PyList_Size(m_ptr); }
        bool empty() const { return size() == 0; }
        detail::list_accessor operator[](size_t index) const { return {*this, index}; }
        template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
        detail::item_accessor operator[](T &&o) const {
            return object::operator[](std::forward<T>(o));
        }
        detail::list_iterator begin() const { return {*this, 0}; }
        detail::list_iterator end() const { return {*this, PyList_GET_SIZE(m_ptr)}; }
        template <typename T>
        void append(T &&val) /* py-non-const */ {
            if (PyList_Append(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) != 0) {
                throw error_already_set();
            }
        }
        template <typename IdxType,
                  typename ValType,
                  detail::enable_if_t<std::is_integral<IdxType>::value, int> = 0>
        void insert(const IdxType &index, ValType &&val) /* py-non-const */ {
            if (PyList_Insert(m_ptr,
                              ssize_t_cast(index),
                              detail::object_or_cast(std::forward<ValType>(val)).ptr())
                != 0) {
                throw error_already_set();
            }
        }
    };

    class args : public tuple {
        PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check)
    };
    class kwargs : public dict {
        PYBIND11_OBJECT_DEFAULT(kwargs, dict, PyDict_Check)
    };

    class anyset : public object {
    public:
        PYBIND11_OBJECT(anyset, object, PyAnySet_Check)
        size_t size() const { return static_cast<size_t>(PySet_Size(m_ptr)); }
        bool empty() const { return size() == 0; }
        template <typename T>
        bool contains(T &&val) const {
            auto result = PySet_Contains(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr());
            if (result == -1) {
                throw error_already_set();
            }
            return result == 1;
        }
    };

    class set : public anyset {
    public:
        PYBIND11_OBJECT_CVT(set, anyset, PySet_Check, PySet_New)
        set() : anyset(PySet_New(nullptr), stolen_t{}) {
            if (!m_ptr) {
                pybind11_fail("Could not allocate set object!");
            }
        }
        template <typename T>
        bool add(T &&val) /* py-non-const */ {
            return PySet_Add(m_ptr, detail::object_or_cast(std::forward<T>(val)).ptr()) == 0;
        }
        void clear() /* py-non-const */ { PySet_Clear(m_ptr); }
    };

    class frozenset : public anyset {
    public:
        PYBIND11_OBJECT_CVT(frozenset, anyset, PyFrozenSet_Check, PyFrozenSet_New)
    };

    class function : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(function, object, PyCallable_Check)
        handle cpp_function() const {
            handle fun = detail::get_function(m_ptr);
            if (fun && PyCFunction_Check(fun.ptr())) {
                return fun;
            }
            return handle();
        }
        bool is_cpp_function() const { return (bool) cpp_function(); }
    };

    class staticmethod : public object {
    public:
        PYBIND11_OBJECT_CVT(staticmethod, object, detail::PyStaticMethod_Check, PyStaticMethod_New)
    };

    class buffer : public object {
    public:
        PYBIND11_OBJECT_DEFAULT(buffer, object, PyObject_CheckBuffer)

        buffer_info request(bool writable = false) const {
            int flags = PyBUF_STRIDES | PyBUF_FORMAT;
            if (writable) {
                flags |= PyBUF_WRITABLE;
            }
            auto *view = new Py_buffer();
            if (PyObject_GetBuffer(m_ptr, view, flags) != 0) {
                delete view;
                throw error_already_set();
            }
            return buffer_info(view);
        }
    };

    class memoryview : public object {
    public:
        PYBIND11_OBJECT_CVT(memoryview, object, PyMemoryView_Check, PyMemoryView_FromObject)

        /** \rst
            Creates ``memoryview`` from ``buffer_info``.

            ``buffer_info`` must be created from ``buffer::request()``. Otherwise
            throws an exception.

            For creating a ``memoryview`` from objects that support buffer protocol,
            use ``memoryview(const object& obj)`` instead of this constructor.
         \endrst */
        explicit memoryview(const buffer_info &info) {
            if (!info.view()) {
                pybind11_fail("Prohibited to create memoryview without Py_buffer");
            }
            // Note: PyMemoryView_FromBuffer never increments obj reference.
            m_ptr = (info.view()->obj) ? PyMemoryView_FromObject(info.view()->obj)
                                       : PyMemoryView_FromBuffer(info.view());
            if (!m_ptr) {
                pybind11_fail("Unable to create memoryview from buffer descriptor");
            }
        }

        /** \rst
            Creates ``memoryview`` from static buffer.

            This method is meant for providing a ``memoryview`` for C/C++ buffer not
            managed by Python. The caller is responsible for managing the lifetime
            of ``ptr`` and ``format``, which MUST outlive the memoryview constructed
            here.

            See also: Python C API documentation for `PyMemoryView_FromBuffer`_.

            .. _PyMemoryView_FromBuffer:
               https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromBuffer

            :param ptr: Pointer to the buffer.
            :param itemsize: Byte size of an element.
            :param format: Pointer to the null-terminated format string. For
                homogeneous Buffers, this should be set to
                ``format_descriptor<T>::value``.
            :param shape: Shape of the tensor (1 entry per dimension).
            :param strides: Number of bytes between adjacent entries (for each
                per dimension).
            :param readonly: Flag to indicate if the underlying storage may be
                written to.
         \endrst */
        static memoryview from_buffer(void *ptr,
                                      ssize_t itemsize,
                                      const char *format,
                                      detail::any_container<ssize_t> shape,
                                      detail::any_container<ssize_t> strides,
                                      bool readonly = false);

        static memoryview from_buffer(const void *ptr,
                                      ssize_t itemsize,
                                      const char *format,
                                      detail::any_container<ssize_t> shape,
                                      detail::any_container<ssize_t> strides) {
            return memoryview::from_buffer(
                const_cast<void *>(ptr), itemsize, format, std::move(shape), std::move(strides), true);
        }

        template <typename T>
        static memoryview from_buffer(T *ptr,
                                      detail::any_container<ssize_t> shape,
                                      detail::any_container<ssize_t> strides,
                                      bool readonly = false) {
            return memoryview::from_buffer(reinterpret_cast<void *>(ptr),
                                           sizeof(T),
                                           format_descriptor<T>::value,
                                           std::move(shape),
                                           std::move(strides),
                                           readonly);
        }

        template <typename T>
        static memoryview from_buffer(const T *ptr,
                                      detail::any_container<ssize_t> shape,
                                      detail::any_container<ssize_t> strides) {
            return memoryview::from_buffer(
                const_cast<T *>(ptr), std::move(shape), std::move(strides), true);
        }

        /** \rst
            Creates ``memoryview`` from static memory.

            This method is meant for providing a ``memoryview`` for C/C++ buffer not
            managed by Python. The caller is responsible for managing the lifetime
            of ``mem``, which MUST outlive the memoryview constructed here.

            See also: Python C API documentation for `PyMemoryView_FromBuffer`_.

            .. _PyMemoryView_FromMemory:
               https://docs.python.org/c-api/memoryview.html#c.PyMemoryView_FromMemory
         \endrst */
        static memoryview from_memory(void *mem, ssize_t size, bool readonly = false) {
            PyObject *ptr = PyMemoryView_FromMemory(
                reinterpret_cast<char *>(mem), size, (readonly) ? PyBUF_READ : PyBUF_WRITE);
            if (!ptr) {
                pybind11_fail("Could not allocate memoryview object!");
            }
            return memoryview(object(ptr, stolen_t{}));
        }

        static memoryview from_memory(const void *mem, ssize_t size) {
            return memoryview::from_memory(const_cast<void *>(mem), size, true);
        }

    #ifdef PYBIND11_HAS_STRING_VIEW
        static memoryview from_memory(std::string_view mem) {
            return from_memory(const_cast<char *>(mem.data()), static_cast<ssize_t>(mem.size()), true);
        }
    #endif
    };

    /// @cond DUPLICATE
    inline memoryview memoryview::from_buffer(void *ptr,
                                              ssize_t itemsize,
                                              const char *format,
                                              detail::any_container<ssize_t> shape,
                                              detail::any_container<ssize_t> strides,
                                              bool readonly) {
        size_t ndim = shape->size();
        if (ndim != strides->size()) {
            pybind11_fail("memoryview: shape length doesn't match strides length");
        }
        ssize_t size = ndim != 0u ? 1 : 0;
        for (size_t i = 0; i < ndim; ++i) {
            size *= (*shape)[i];
        }
        Py_buffer view;
        view.buf = ptr;
        view.obj = nullptr;
        view.len = size * itemsize;
        view.readonly = static_cast<int>(readonly);
        view.itemsize = itemsize;
        view.format = const_cast<char *>(format);
        view.ndim = static_cast<int>(ndim);
        view.shape = shape->data();
        view.strides = strides->data();
        view.suboffsets = nullptr;
        view.internal = nullptr;
        PyObject *obj = PyMemoryView_FromBuffer(&view);
        if (!obj) {
            throw error_already_set();
        }
        return memoryview(object(obj, stolen_t{}));
    }
    /// @endcond
    /// @} pytypes

    /// \addtogroup python_builtins
    /// @{

    /// Get the length of a Python object.
    inline size_t len(handle h) {
        ssize_t result = PyObject_Length(h.ptr());
        if (result < 0) {
            throw error_already_set();
        }
        return (size_t) result;
    }

    /// Get the length hint of a Python object.
    /// Returns 0 when this cannot be determined.
    inline size_t len_hint(handle h) {
        ssize_t result = PyObject_LengthHint(h.ptr(), 0);
        if (result < 0) {
            // Sometimes a length can't be determined at all (eg generators)
            // In which case simply return 0
            PyErr_Clear();
            return 0;
        }
        return (size_t) result;
    }

    inline str repr(handle h) {
        PyObject *str_value = PyObject_Repr(h.ptr());
        if (!str_value) {
            throw error_already_set();
        }
        return reinterpret_steal<str>(str_value);
    }

    inline iterator iter(handle obj) {
        PyObject *result = PyObject_GetIter(obj.ptr());
        if (!result) {
            throw error_already_set();
        }
        return reinterpret_steal<iterator>(result);
    }
    /// @} python_builtins

    PYBIND11_NAMESPACE_BEGIN(detail)
    template <typename D>
    iterator object_api<D>::begin() const {
        return iter(derived());
    }
    template <typename D>
    iterator object_api<D>::end() const {
        return iterator::sentinel();
    }
    template <typename D>
    item_accessor object_api<D>::operator[](handle key) const {
        return {derived(), reinterpret_borrow<object>(key)};
    }
    template <typename D>
    item_accessor object_api<D>::operator[](object &&key) const {
        return {derived(), std::move(key)};
    }
    template <typename D>
    item_accessor object_api<D>::operator[](const char *key) const {
        return {derived(), pybind11::str(key)};
    }
    template <typename D>
    obj_attr_accessor object_api<D>::attr(handle key) const {
        return {derived(), reinterpret_borrow<object>(key)};
    }
    template <typename D>
    obj_attr_accessor object_api<D>::attr(object &&key) const {
        return {derived(), std::move(key)};
    }
    template <typename D>
    str_attr_accessor object_api<D>::attr(const char *key) const {
        return {derived(), key};
    }
    template <typename D>
    args_proxy object_api<D>::operator*() const {
        return args_proxy(derived().ptr());
    }
    template <typename D>
    template <typename T>
    bool object_api<D>::contains(T &&item) const {
        return attr("__contains__")(std::forward<T>(item)).template cast<bool>();
    }

    template <typename D>
    pybind11::str object_api<D>::str() const {
        return pybind11::str(derived());
    }

    template <typename D>
    str_attr_accessor object_api<D>::doc() const {
        return attr("__doc__");
    }

    template <typename D>
    handle object_api<D>::get_type() const {
        return type::handle_of(derived());
    }

    template <typename D>
    bool object_api<D>::rich_compare(object_api const &other, int value) const {
        int rv = PyObject_RichCompareBool(derived().ptr(), other.derived().ptr(), value);
        if (rv == -1) {
            throw error_already_set();
        }
        return rv == 1;
    }

    #define PYBIND11_MATH_OPERATOR_UNARY(op, fn)                                                      \
        template <typename D>                                                                         \
        object object_api<D>::op() const {                                                            \
            object result = reinterpret_steal<object>(fn(derived().ptr()));                           \
            if (!result.ptr())                                                                        \
                throw error_already_set();                                                            \
            return result;                                                                            \
        }

    #define PYBIND11_MATH_OPERATOR_BINARY(op, fn)                                                     \
        template <typename D>                                                                         \
        object object_api<D>::op(object_api const &other) const {                                     \
            object result = reinterpret_steal<object>(fn(derived().ptr(), other.derived().ptr()));    \
            if (!result.ptr())                                                                        \
                throw error_already_set();                                                            \
            return result;                                                                            \
        }

    #define PYBIND11_MATH_OPERATOR_BINARY_INPLACE(iop, fn)                                            \
        template <typename D>                                                                         \
        object object_api<D>::iop(object_api const &other) {                                          \
            object result = reinterpret_steal<object>(fn(derived().ptr(), other.derived().ptr()));    \
            if (!result.ptr())                                                                        \
                throw error_already_set();                                                            \
            return result;                                                                            \
        }

    PYBIND11_MATH_OPERATOR_UNARY(operator~, PyNumber_Invert)
    PYBIND11_MATH_OPERATOR_UNARY(operator-, PyNumber_Negative)
    PYBIND11_MATH_OPERATOR_BINARY(operator+, PyNumber_Add)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator+=, PyNumber_InPlaceAdd)
    PYBIND11_MATH_OPERATOR_BINARY(operator-, PyNumber_Subtract)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator-=, PyNumber_InPlaceSubtract)
    PYBIND11_MATH_OPERATOR_BINARY(operator*, PyNumber_Multiply)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator*=, PyNumber_InPlaceMultiply)
    PYBIND11_MATH_OPERATOR_BINARY(operator/, PyNumber_TrueDivide)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator/=, PyNumber_InPlaceTrueDivide)
    PYBIND11_MATH_OPERATOR_BINARY(operator|, PyNumber_Or)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator|=, PyNumber_InPlaceOr)
    PYBIND11_MATH_OPERATOR_BINARY(operator&, PyNumber_And)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator&=, PyNumber_InPlaceAnd)
    PYBIND11_MATH_OPERATOR_BINARY(operator^, PyNumber_Xor)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator^=, PyNumber_InPlaceXor)
    PYBIND11_MATH_OPERATOR_BINARY(operator<<, PyNumber_Lshift)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator<<=, PyNumber_InPlaceLshift)
    PYBIND11_MATH_OPERATOR_BINARY(operator>>, PyNumber_Rshift)
    PYBIND11_MATH_OPERATOR_BINARY_INPLACE(operator>>=, PyNumber_InPlaceRshift)

    #undef PYBIND11_MATH_OPERATOR_UNARY
    #undef PYBIND11_MATH_OPERATOR_BINARY
    #undef PYBIND11_MATH_OPERATOR_BINARY_INPLACE

    PYBIND11_NAMESPACE_END(detail)
    PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)