def assertFullyNewStyle(self, instance):
        """
        Assert that the given object is an instance of a new-style class and
        that there are no classic classes in the inheritance hierarchy of
        that class.

        This is a beneficial condition because PyPy is better able to
        optimize attribute lookup on such classes.
        """
        self.assertIsInstance(instance, object)
        mro = inspect.getmro(type(instance))
        for subclass in mro:
            self.assertTrue(
                issubclass(subclass, object),
                "%r is not new-style" % (subclass,))

        Assert that the given object is an instance of a new-style class and
        that there are no classic classes in the inheritance hierarchy of
        that class.

        This is a beneficial condition because PyPy is better able to
        optimize attribute lookup on such classes.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/test/test_core.py