def test_failureElementTraceback(self):
        """
        The I{traceback} renderer of L{FailureElement} renders the failure's
        stack frames using L{_StackElement}.
        """
        element = FailureElement(self.failure)
        renderer = element.lookupRenderMethod("traceback")
        tag = tags.div()
        result = renderer(None, tag)
        self.assertIsInstance(result, _StackElement)
        self.assertIdentical(result.stackFrames, self.failure.frames)
        self.assertEqual([tag], result.loader.load())

        The I{traceback} renderer of L{FailureElement} renders the failure's
        stack frames using L{_StackElement}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_util.py