def process(self):
        """
        Handle this request by connecting to the proxied server and forwarding
        it there, then forwarding the response back as the response to this
        request.
        """
        self.requestHeaders.setRawHeaders(b"host",
                                          [self.factory.host.encode('ascii')])
        clientFactory = self.proxyClientFactoryClass(
            self.method, self.uri, self.clientproto, self.getAllHeaders(),
            self.content.read(), self)
        self.reactor.connectTCP(self.factory.host, self.factory.port,
                                clientFactory)

        Handle this request by connecting to the proxied server and forwarding
        it there, then forwarding the response back as the response to this
        request.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/proxy.py