def test_formatAlreadySet(self):
        """
        Formatting is not altered if the old-style C{"format"} key already
        exists.
        """
        event = self.forwardAndVerify(
            dict(log_format="Hello!", format="Howdy!")
        )
        self.assertEqual(legacyLog.textFromEventDict(event), "Howdy!")

        Formatting is not altered if the old-style C{"format"} key already
        exists.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_legacy.py