def get_function_notification_session(self, function_receiver=None):
raise Unimplemented()<EOL>
Gets the notification session for notifications pertaining to function changes.

        arg:    function_receiver (osid.authorization.FunctionReceiver):
                the function receiver
        return: (osid.authorization.FunctionNotificationSession) - a
                ``FunctionNotificationSession``
        raise:  NullArgument - ``function_receiver`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_function_notification()`` is
                ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_function_notification()`` is ``true``.*