def test_frameElementSource(self):
        """
        The I{source} renderer of L{_FrameElement} renders the source code near
        the source filename/line number associated with the frame object used to
        initialize the L{_FrameElement}.
        """
        element = _FrameElement(None, self.frame)
        renderer = element.lookupRenderMethod("source")
        tag = tags.div()
        result = renderer(None, tag)
        self.assertIsInstance(result, _SourceFragmentElement)
        self.assertIdentical(result.frame, self.frame)
        self.assertEqual([tag], result.loader.load())

        The I{source} renderer of L{_FrameElement} renders the source code near
        the source filename/line number associated with the frame object used to
        initialize the L{_FrameElement}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_util.py