def test_flattenEventWithInertFormat(self):
        """
        L{flattenEvent} will do nothing to an event with a format string that
        contains no format fields.
        """
        inputEvent = {'a': 'b', 'c': 1, 'log_format': 'simple message'}
        flattenEvent(inputEvent)
        self.assertEqual(
            inputEvent,
            {
                'a': 'b',
                'c': 1,
                'log_format': 'simple message',
            }
        )

        L{flattenEvent} will do nothing to an event with a format string that
        contains no format fields.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/logger/test/test_flatten.py