src/Controller/Plugin/Notification.php
public function addMessage($message, $namespace = self::NAMESPACE_INFO)
    {
        if (!$message instanceof NotificationEntityInterface) {
            $messageText = $this->isTranslatorEnabled()
                ? $this->getTranslator()->translate($message, $this->getTranslatorTextDomain())
                : $message;

            $message = new NotificationEntity();
            $message->setNotification($messageText);
            $message->setPriority($this->namespace2priority[$namespace]);
        }
        $nEvent = new NotificationEvent();
        $nEvent->setNotification($message);
        $this->notificationListener->trigger(NotificationEvent::EVENT_NOTIFICATION_ADD, $nEvent);

        return $this;
    }
public function addMessage($message, $namespace = self::NAMESPACE_INFO)
    {
        if (!$message instanceof NotificationEntityInterface) {
            $messageText = $this->isTranslatorEnabled()
                ? $this->getTranslator()->translate($message, $this->getTranslatorTextDomain())
                : $message;

            $message = new NotificationEntity();
            $message->setNotification($messageText);
            $message->setPriority($this->namespace2priority[$namespace]);
        }
        $nEvent = new NotificationEvent();
        $nEvent->setNotification($message);
        $this->notificationListener->trigger(NotificationEvent::EVENT_NOTIFICATION_ADD, $nEvent);

        return $this;
    }
send a message to the notification-handler
@param $message
@param string $namespace
@return $this