def update_machine(self, system_id, params):
        """Update a specific Machine.

        http://maas.ubuntu.com/docs2.0/api.html#machine

        :param system_id to identify the machine
        :param params: params to update
        """
        url = u'machines/{system_id}/'.format(system_id=system_id)
        res = self.put(url, params)
        return res