def test_noSubcommand(self):
        """
        If no subcommand is specified and no default subcommand is assigned,
        a subcommand will not be implied.
        """
        o = SubCommandOptions()
        o.parseOptions(['--europian-swallow'])
        self.assertTrue(o['europian-swallow'])
        self.assertIsNone(o.subCommand)
        self.assertFalse(hasattr(o, 'subOptions'))

        If no subcommand is specified and no default subcommand is assigned,
        a subcommand will not be implied.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_usage.py