Method cast

include/pybind11/cast.h:898–901

    explicit operator holder_type &() { return holder; }

    static handle cast(const holder_type &src, return_value_policy, handle) {
        const auto *ptr = holder_helper<holder_type>::get(src);
        return type_caster_base<type>::cast_holder(ptr, &src);
    }

protected:
    friend class type_caster_generic;