code: def find_for_event(cls, event, include_hidden=False, **kwargs):
          
          query = cls.find(event_id=event.id, **kwargs)
          if not include_hidden:
              query = query.filter(~cls.hidden)
          return query
docs: Returns a Query that retrieves the chatrooms for an event
  
          :param event: an indico event (with a numeric ID)
          :param include_hidden: if hidden chatrooms should be included, too
          :param kwargs: extra kwargs to pass to ``find()``