def test_noMessageNoFormat(self):
        """
        If C{"format"} is unspecified and C{"message"} is empty, return
        L{None}.
        """
        eventDict = dict(message=(), isError=0)
        text = log.textFromEventDict(eventDict)
        self.assertIsNone(text)

        If C{"format"} is unspecified and C{"message"} is empty, return
        L{None}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_log.py