code: def is_bridge(self):
          
          # Since this does not change over time (?) check whether we already
          # know the answer. If so, there is no need to go further
          if self._is_bridge is not None:
              return self._is_bridge
          # if not, we have to get it from the zone topology. This will set
          # self._is_bridge for us for next time, so we won't have to do this
          # again
          self._parse_zone_group_state()
          return self._is_bridge
docs: bool: Is this zone a bridge?