code: func (c *Client) Noop() (err error) {
  	res := struct {
  		Status string `xmlrpc:"status"`
  	}{}
  	err = c.Call("NoOperation", []interface{}{c.Token}, &res)
  	if err == nil && res.Status != StatusSuccess {
  		err = fmt.Errorf("NoOp: %s", res.Status)
  	}
  	return
  }
docs: // Noop keeps a session alive.