human
Can you provide a the Python code you requested given the following:
Complete the below
def _AddSetListenerMethod(cls):

    ''''Helper for _AddMessageMethods().'
    '''
assistant
#Here is the Python code you requested.
    def SetListener(self, listener):
        if (listener is None):
            self._listener = message_listener_mod.NullMessageListener()
        else:
            self._listener = listener
    cls._SetListener = SetListener