def test_getRawHeadersDefaultValue(self):
        """
        L{Headers.getRawHeaders} returns the specified default value when no
        header is found.
        """
        h = Headers()
        default = object()
        self.assertIdentical(h.getRawHeaders(u"test", default), default)
        self.assertIdentical(h.getRawHeaders(u"test", None), None)
        self.assertEqual(h.getRawHeaders(u"test", [None]), [None])
        self.assertEqual(
            h.getRawHeaders(u"test", [u"\N{SNOWMAN}"]),
            [u"\N{SNOWMAN}"],
        )

        L{Headers.getRawHeaders} returns the specified default value when no
        header is found.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_http_headers.py