code: def _get_loop(self):
          
          # we import and assign the default here (and not, e.g., when
          # making Config) so as to delay importing reactor as long as
          # possible in case someone is installing a custom one.
          if self._config.loop is None:
              from twisted.internet import reactor
              self._config.loop = reactor
          return self._config.loop
docs: internal helper