def yaml(self):
        return yaml.dump(self.serialized, default_flow_style=False,
                         encoding=None)
def test_exceptions(self):
        self.assert_(issubclass(DeoptionError, TypeError))
        self.assertRaises(TypeError,
            lambda: Optional()
        )
        self.assertRaises(TypeError,
            lambda: Optional(NotPassed, NotPassed)
        )