def test_caseInsensitiveComparison(self):
        """
        L{dns._isSubdomainOf} does case-insensitive comparison
        of name labels.
        """
        assertIsSubdomainOf(self, b'foo.example.com', b'EXAMPLE.COM')

        assertIsSubdomainOf(self, b'FOO.EXAMPLE.COM', b'example.com')

        L{dns._isSubdomainOf} does case-insensitive comparison
        of name labels.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/names/test/test_dns.py