docs: def can_be_registered(self, event_type):
          """Checks if the event can be registered/subscribed to.
  
          :param event_type: event that needs to be verified
          :returns: whether the event can be registered/subscribed to
          :rtype: boolean
          """
          return (event_type in self._watchable_events or
                  (event_type == self.ANY and self._allow_any))