code: def is_sensor(self, sensorid, child_id=None):
          
          ret = sensorid in self.sensors
          if not ret:
              _LOGGER.warning('Node %s is unknown', sensorid)
          if ret and child_id is not None:
              ret = child_id in self.sensors[sensorid].children
              if not ret:
                  _LOGGER.warning('Child %s is unknown', child_id)
          if not ret and parse_ver(self.protocol_version) >= parse_ver('2.0'):
              _LOGGER.info('Requesting new presentation for node %s',
                           sensorid)
              msg = Message(gateway=self).modify(
                  node_id=sensorid, child_id=SYSTEM_CHILD_ID,
                  type=self.const.MessageType.internal,
                  sub_type=self.const.Internal.I_PRESENTATION)
              if self._route_message(msg):
                  self.add_job(msg.encode)
          return ret
docs: Return True if a sensor and its child exist.