code: def _on_trace(self, sequence, topic, message):
          
  
          try:
              conn_key = self._find_connection(topic)
              conn_id = self.conns.get_connection_id(conn_key)
          except ArgumentError:
              self._logger.warn("Dropping trace message that does not correspond with a known connection, topic=%s", topic)
              return
  
          try:
              tracing = messages.TracingNotification.verify(message)
              self._trigger_callback('on_trace', conn_id, tracing['trace'])
          except Exception:
              self._logger.exception("Error processing trace conn_id=%d", conn_id)
docs: Process a trace received from a device.
  
          Args:
              sequence (int): The sequence number of the packet received
              topic (string): The topic this message was received on
              message (dict): The message itself