def test_forward(self):
        """
        When connected to the server, L{ProxyClient} should send the saved
        request, with modifications of the headers, and then forward the result
        to the parent request.
        """
        return self._testDataForward(
            200, b"OK", [(b"Foo", [b"bar", b"baz"])], b"Some data\r\n")

        When connected to the server, L{ProxyClient} should send the saved
        request, with modifications of the headers, and then forward the result
        to the parent request.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_proxy.py