public function beforeValidate($event)
    {
        $formName = $event->sender->formName();
        $primaryKey = $event->sender->primaryKey;

        /** @var ActiveRecord $sender */
        $sender = $event->sender;

        /** @var MetaTags $metaTags */
        $metaTags = $sender->{$this->relationName};
        if (!$metaTags) {
            $metaTags = Yii::createObject(MetaTags::class);
            $metaTags->model = $formName;
            $metaTags->model_id = $primaryKey;
            $metaTags->language = $this->lang();
            $metaTags->load(Yii::$app->request->post());
        }

        $sender->populateRelation($this->relationName, $metaTags);
    }