def test_noCalls(self):
        """
        If there are no delayed calls, C{doIteration} is called with a
        timeout of L{None}.
        """
        reactor = TimeoutReportReactor()
        timeout = self._checkIterationTimeout(reactor)
        self.assertIsNone(timeout)

        If there are no delayed calls, C{doIteration} is called with a
        timeout of L{None}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_posixbase.py