notification;

        for (key in this._notifications) {
            if (this._notifications.hasOwnProperty(key)) {
                notification = this._notifications[key];

                /* Run only if the tags match */
                if (notification.tag === tag) {
                    /* Call the notification's close() method */
                    return this._closeNotification(key);
                }
            }
        }
Closes a notification with the given tag
@param {String} tag - Tag of the notification to close
@return {Boolean} boolean denoting success