code: def request_done(self, request):
          
          if self._requests is None:
              # Channel been cleaned up because the connection was lost.
              return
  
          assert request == self._requests[0], "Unexpected request done"
          del self._requests[0]
  
          if request.persistent:
              # Activate the next request in the pipeline if any
              if self._requests:
                  self._requests[0].activate()
          else:
              self.transport.loseConnection()
docs: Called by the active request when it is done writing