def test_repr(self):
        """
        The L{repr} of a L{Headers} instance shows the names and values of all
        the headers it contains.
        """
        foo = b"foo"
        bar = b"bar"
        baz = b"baz"
        self.assertEqual(
            repr(Headers({foo: [bar, baz]})),
            "Headers({%r: [%r, %r]})" % (foo, bar, baz))

        The L{repr} of a L{Headers} instance shows the names and values of all
        the headers it contains.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_http_headers.py