code: function(callback) {
          /**
           * Callback for QB.pushnotifications.subscriptions.list(callback)
           * @callback listPushSubscriptionCallback
           * @param {object} error - The error object
           * @param {object} response - Array of all existent user's subscriptions
           */
          this.service.ajax({url: Utils.getUrl(config.urls.subscriptions)}, callback);
      }
docs: Retrieve subscriptions for the user which is specified in the session token ({@link https://docsdev.quickblox.com/rest_api/Push_Notifications_API.html#Retrieve_subscriptions read more})
  @memberof QB.pushnotifications.subscriptions
  @param {listPushSubscriptionCallback} callback - The listPushSubscriptionCallback function