code: def _connectionLost(self, reason):
          
          log.info('%r: Connection closed: %r', self, reason)
  
          # Reset our proto so we don't try to send to a down connection
          self.proto = None
  
          # Mark any in-flight requests as unsent.
          for tReq in self.requests.values():
              tReq.sent = False
  
          if self._dDown:
              self._dDown.callback(None)
          elif self.requests:
              self._connect()
docs: Called when the protocol connection is lost
  
          - Log the disconnection.
          - Mark any outstanding requests as unsent so they will be sent when
            a new connection is made.
          - If closing the broker client, mark completion of that process.
  
          :param reason:
              Failure that indicates the reason for disconnection.