Can not cast custom struct to python obj

[Roy-Kid]

Hi anyone,

I want to convert my custom structure to python object. Here is what impl in c++

// data in dict
template <typename... Ts>
class Data
{
public:
    using variant_type = std::variant<Ts...>;

    Data() : _value(variant_type{}) {}

    template <typename T>
    Data(const T &value) : _value(value) {}

    template <typename T>
    Data<Ts...> &operator=(const T &V)
    {

        _value = V;
        return *this;
    }

    template<typename... Us>
    bool operator==(const Data<Us...>& other) const
    {
        if (_value.index() != other.get_variant().index())
            return false;
        return _value == other.get_variant();
    }

    template <typename T>
    T &get()
    {
        return std::get<T>(_value);
    }

    template <typename T>
    const T &get() const
    {
        return std::get<T>(_value);
    }

    // set
    void set(const variant_type &V)
    {
        _value = V;
    }

    template <typename T>
    bool is() const
    {
        return std::holds_alternative<T>(_value);
    }

    variant_type _value;

    const auto index() const
    {
        return _value.index();
    }

    variant_type get_variant() const
    {
        return _value;
    }
};

What I want to do is try to convert this structure to python built-in object automatically. Thus I define a type_caster like this:

#include <pybind11/pybind11.h>
#include <pybind11/stl.h>
#include <pybind11/cast.h>
#include "dict.h"
#include <iostream>

using TypedData = Data<int, std::string>;

namespace py = pybind11;

namespace pybind11
{
    namespace detail
    {

        template <>
        struct type_caster<TypedData>
        {
        public:
            PYBIND11_TYPE_CASTER(TypedData, const_name("TypedData"));

            static handle cast(const TypedData &d, return_value_policy, handle)
            {
                switch (d.index())
                {
                case 0:
                    return py::cast(d.get<int>()).inc_ref();
                case 1:
                    return py::cast(d.get<std::string>()).inc_ref();
                }

                throw std::runtime_error("Unreachable");
            }

            // 判断Python对象是否可以转换为C++对象
            bool load(handle src, bool)
            {
                if (isinstance<py::int_>(src))
                {
                    value = TypedData(py::cast<int>(src));
                }
                else if (isinstance<py::str>(src))
                {
                    value = TypedData(py::cast<std::string>(src));
                }
                else
                    return false;
                return true;
            }
        };

    } // namespace detail
} // namespace pybind11

PYBIND11_MODULE(example, m)
{
    py::class_<TypedData>(m, "TypedData")
        .def(py::init<std::variant<int, std::string>>());

}

But when I try to access Data in python, it always return a object not built-in object

In [1]: import example

In [2]: a = example.TypedData(42)

In [3]: a
Out[3]: <example.TypedData at 0x7f6c98aaa1b0>  # I want to it return int or str 

Where I did wrong? Can someone help me with it?
Thanks !!!!!!!