def test_formatRootTagNoFilename(self):
        """
        The C{_formatRoot} method formats a C{Tag} with no filename information
        as 'Tag <tagName>'.
        """
        e = self.makeFlattenerError()
        self.assertEqual(e._formatRoot(Tag('a-tag')), 'Tag <a-tag>')

        The C{_formatRoot} method formats a C{Tag} with no filename information
        as 'Tag <tagName>'.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_error.py