skeeks\cms\models\CmsContentElement::validateParentContentElement PHP Method

    public function validateParentContentElement($attribute)
    {
        if (!$this->cmsContent) {
            return false;
        }
        if (!$this->cmsContent->parentContent) {
            return false;
        }
        if ($this->{$attribute}) {
            $contentElement = static::findOne($this->{$attribute});
            if ($contentElement->cmsContent->id != $this->cmsContent->parentContent->id) {
                $this->addError($attribute, \Yii::t('skeeks/cms', 'The parent must be a content element: «{contentName}».', ['contentName' => $this->cmsContent->parentContent->name]));
            }
        }
    }