SWIG interface with using of Python callable as callback

something.i

%module(threads="1") something

%{
// Register a callback (called from Python code)
// callbackFunc is a Python callable accepting one argument
void registerHandler(PyObject *callbackFunc)
{
    SWIG_PYTHON_THREAD_BEGIN_ALLOW;
    
    const bool hasCallback = 
        callbackFunc != 0 && callbackFunc != Py_None;
    
    // do registration of 'callbackFunc' ...

    SWIG_PYTHON_THREAD_END_ALLOW;
    
    Py_XINCREF(callbackFunc); // to keep callback alive, don't forget to DECREF on unregiser
}

// Calls the callback (called from C code), Param is some SWIG-wrapped type
void processCallback(PyObject *callbackFunc, Param& param)
{
    SWIG_PYTHON_THREAD_BEGIN_BLOCK;

    PyObject *arglist = PyTuple_New(1);
    PyTuple_SET_ITEM(arglist, 0, 
        SWIG_NewPointerObj(SWIG_as_voidptr(&param), SWIGTYPE_p_Param_Type, 0));
    
    PyObject *result = PyEval_CallObject(callbackFunc, arglist);
    
    Py_DECREF(arglist);
    Py_XDECREF(result);

    SWIG_PYTHON_THREAD_END_BLOCK;
}
%}

%typemap(in) PyObject * {
    $1 = $input;
}

%typemap(out) PyObject * {
    $result = $1;
}

%nothread registerHandler;
void registerHandler(PyObject *callbackFunc);