def test_datetimeRoundtrip(self):

        """
        If an L{xmlrpclib.DateTime} is passed as an argument to an XML-RPC
        call and then returned by the server unmodified, the result should
        be equal to the original object.
        """
        when = xmlrpclib.DateTime()
        d = self.proxy().callRemote("echo", when)
        d.addCallback(self.assertEqual, when)
        return d

        If an L{xmlrpclib.DateTime} is passed as an argument to an XML-RPC
        call and then returned by the server unmodified, the result should
        be equal to the original object.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_xmlrpc.py