public function removeNotificationListener($notification_id)
    {
        foreach ($this->_notifications as $notification_type => $notifications) {
            foreach (array_keys($notifications) as $id) {
                if ($notification_id == $id) {
                    unset($this->_notifications[$notification_type][$id]);
                    $this->_logger->log(Logger::INFO, "Callback with notification ID '{$notification_id}' has been removed.");
                    return true;
                }
            }
        }

        $this->_logger->log(Logger::DEBUG, "No Callback found with notification ID '{$notification_id}'.");
        return false;
    }