def _unmakeHelperReactor(self):
        """
        Stop and discard the reactor started by C{_makeHelperReactor}.
        """
        self._reactor.callFromThread(self._reactor.stop)
        self._reactor = None

        Stop and discard the reactor started by C{_makeHelperReactor}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/win32eventreactor.py