pybind11 getting arguments in c++

example.cpp

#include <pybind11/pybind11.h>

namespace py = pybind11;

template<typename T>
T get_argument(const char* name, int& index, const py::args& args, const py::kwargs& kwargs)
{
    if(kwargs.contains(name))
    {
        return kwargs[name].cast<T>();   
    }
    else if(py::len(args) > index)
    {
        return args[index++].cast<T>();
    }
    throw std::invalid_argument(std::string(name) + " is a required parameter");
}

PYBIND11_MODULE(example, m){
    m.doc() = "Pybind11 example plugin";
    m.def("add", [](int foo = 0, py::args args, py::kwargs kw){
        int args_idx = 0;
        auto key = get_argument<py::buffer>("key", args_idx, args, kw);
        auto iv = get_argument<py::buffer>("iv", args_idx, args, kw);
        return foo;
    }, py::arg("foo") = 0, "A function to add two numbers");
}