def unregisterMachine(self, machineName):
        """
        This operation unregisters a portal machine from a portal site. The
        operation can only performed when there are two machines
        participating in a portal site.
        """
        url = self._url + "/machines/unregister"
        params = {
            "f" : "json",
            "machineName" : machineName
        }
        return self._post(url=url,
                          param_dict=params,
                          proxy_url=self._proxy_url,
                          proxy_port=self._proxy_port)
This operation unregisters a portal machine from a portal site. The
        operation can only performed when there are two machines
        participating in a portal site.