code: public function handle(GetPropertyOptionsEvent $event)
      {
          if (!$this->wantToHandle($event) || ($event->getPropertyName() !== 'template')) {
              return;
          }
  
          $model     = $event->getModel();
          $metaModel = $this->getMetaModelFromModel($model);
          $attribute = $metaModel->getAttributeById($model->getProperty('attr_id'));
  
          if (!$attribute) {
              return;
          }
  
          $event->setOptions($this->templateList->getTemplatesForBase('mm_attr_' . $attribute->get('type')));
      }
docs: Retrieve the options for the attributes.
  
  @param GetPropertyOptionsEvent $event The event.
  
  @return void