def proxy(self, factory=None):
        """
        Return a new xmlrpc.Proxy for the test site created in
        setUp(), using the given factory as the queryFactory, or
        self.queryFactory if no factory is provided.
        """
        p = xmlrpc.Proxy(networkString("http://127.0.0.1:%d/" % self.port))
        if factory is None:
            p.queryFactory = self.queryFactory
        else:
            p.queryFactory = factory
        return p

        Return a new xmlrpc.Proxy for the test site created in
        setUp(), using the given factory as the queryFactory, or
        self.queryFactory if no factory is provided.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_xmlrpc.py