Cause the callbacks associated with the event to be called
        :param event: the event that occurred
        :type event: str
        :param data: optional data to pass to the callback
        :type data: anything that should be passed to the callback

def trigger (self, event, *args, **kwargs):
        """
        Cause the callbacks associated with the event to be called
        :param event: the event that occurred
        :type event: str
        :param data: optional data to pass to the callback
        :type data: anything that should be passed to the callback
        """
        if self._events.has_key(event):
            for _callback in self._events[event]:
                try:
                    _callback(args, kwargs)
                except TypeError:
                    _callback()