Wrapper to call a list's method from one of the events

def _modify_event(self, event_name, method, func):
        """
        Wrapper to call a list's method from one of the events
        """
        if event_name not in self.ALL_EVENTS:
            raise TypeError(('event_name ("%s") can only be one of the '
                             'following: %s') % (event_name,
                                                 repr(self.ALL_EVENTS)))
        if not isinstance(func, collections.Callable):
            raise TypeError(('func must be callable to be added as an '
                             'observer.'))
        getattr(self._events[event_name], method)(func)