'Update volume\'s properties. None value keeps the current value.'

def update_volume(self, name, new_name=None, description=None, size=None, history_policy=None):

    cmd = RdxApiCmd(cmd_prefix=[VOLUMES, UPDATE_COMMAND])
    cmd.set_argument(name)
    cmd.add_flag('size', size)
    cmd.add_flag('new-name', new_name)
    cmd.add_flag('policy', history_policy)
    cmd.add_flag('size', size)
    cmd.add_flag('description', description)
    self._run_cmd(cmd)
