code: def _disconnect(self, error):
          "done"
          if self._on_disconnect:
              self._on_disconnect(str(error))
          if self._sender:
              self._sender.connectionLost(Failure(error))
          self._when_done.fire(Failure(error)f _disconnect(self, error):
          "done"
          if self._on_disconnect:
              self._on_disconnect(str(error))
          if self._sender:
              self._sender.connectionLost(Failure(error))
          self._when_done.fire(Failure(error))
docs: done