public function releaseMessage($queue_name, $message_id, $reservation_id, $delay)
    {
        $this->setJsonHeaders();
        $queue = rawurlencode($queue_name);
        $params = array('reservation_id' => $reservation_id);
        if ($delay !== 0) {
            $params['delay'] = (int) $delay;
        }
        $url = "projects/{$this->project_id}/queues/$queue/messages/{$message_id}/release";
        return self::json_decode($this->apiCall(self::POST, $url, $params));
    }