Converting a dictionary to unordered_map (without copying)

I am trying to pass a py::dict to a funtion. Internally, inside C++, I want to use unordered_map.
However when I pass a dict of type (int : int), it gives an error : Unable to cast Python instance to C++ type (compile in debug mode for details). Need some help here. I do not want the copy thing to happed and thats why I am using opaque.

PYBIND11_MAKE_OPAQUE(std::unordered_map<int, int>);
namespace py = pybind11;

std::unordered_map<int, int> modify_map(py::dict dictionary) {
    std::unordered_map<int, int> mapp = dictionary.cast<std::unordered_map<int , int>>();  
// DO some stuff here  
return mapp;
}
PYBIND11_MODULE(SYCL, m) {
    m.def("mod", &modify_map);
    py::bind_map<std::unordered_map<int, int>>(m, "IntMap");
}```

Start at the modify_map function and the PYBIND11_MODULE definition shown in the issue, then read the relevant pybind11 dict casting and bind_map documentation or tests. Reproduce the debug-mode cast failure with the provided int-to-int example and determine whether the requested no-copy conversion is supported; done means a documented, verified resolution or a clearly scoped project change.