def test_aybabtuStrict(self):
        """
        For a diamond-shaped inheritance graph, L{styles._aybabtu} returns a
        list containing I{both} intermediate subclasses.
        """
        self.assertEqual(
            styles._aybabtu(VersionedDiamondSubClass),
            [VersionedSubSubClass, VersionedSubClass, SecondVersionedSubClass])

        For a diamond-shaped inheritance graph, L{styles._aybabtu} returns a
        list containing I{both} intermediate subclasses.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/test/test_persisted.py