code: def request_sensor_list(self, req, msg):
          
          if msg.arguments:
              name = (msg.arguments[0],)
              keys = (name, )
              if name not in self.fake_sensor_infos:
                  return ("fail", "Unknown sensor name.")
          else:
              keys = self.fake_sensor_infos.keys()
  
          num_informs = 0
          for sensor_name in keys:
              infos = self.fake_sensor_infos[sensor_name]
              num_informs += 1
              req.inform(sensor_name, *infos)
  
          return ('ok', num_informs)
docs: Sensor list