def test_definedRenderer(self):
        """
        When called with the name of a defined render method,
        L{Element.lookupRenderMethod} returns that render method.
        """
        class ElementWithRenderMethod(Element):
            @renderer
            def foo(self, request, tag):
                return "bar"
        foo = ElementWithRenderMethod().lookupRenderMethod("foo")
        self.assertEqual(foo(None, None), "bar")

        When called with the name of a defined render method,
        L{Element.lookupRenderMethod} returns that render method.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_template.py