def test_loaderClassAttribute(self):
        """
        If there is a non-None loader attribute on the class of an Element
        instance but none on the instance itself, the class attribute is used.
        """
        class SubElement(Element):
            loader = XMLString("<p>Hello, world.</p>")
        return self.assertFlattensTo(SubElement(), b"<p>Hello, world.</p>")

        If there is a non-None loader attribute on the class of an Element
        instance but none on the instance itself, the class attribute is used.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_template.py