def test_usageConsistency(self):
        """
        The example script prints a usage message to stdout if it is
        passed a --help option and then exits.

        The first line should contain a USAGE summary, explaining the
        accepted command arguments.
        """
        # Pass None as first parameter - the reactor - it shouldn't
        # get as far as calling it.
        self.assertRaises(
            SystemExit, self.example.main, None, '--help')

        out = self.fakeOut.getvalue().splitlines()
        self.assertTrue(
            out[0].startswith('Usage:'),
            'Usage message first line should start with "Usage:". '
            'Actual: %r' % (out[0],))

        The example script prints a usage message to stdout if it is
        passed a --help option and then exits.

        The first line should contain a USAGE summary, explaining the
        accepted command arguments.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_examples.py