human
Solve the following python programming problem given the following code:
def _callback(self, cdecl, **kwargs) : 
    'Wrapper for ffi.callback() that keeps callback alive.' 
    def callback_decorator(python_callable) : 
        function_ptr = _ffi.callback (cdecl, python_callable, ** kwargs) 
        self._keepalive.append (function_ptr) 
        return function_ptr 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def callback_decorator(