code: public function handle(GetPropertyOptionsEvent $event)
      {
          if (!$this->wantToHandle($event) || ($event->getPropertyName() !== 'filter')) {
              return;
          }
          $model = $event->getModel();
          $pid   = $model->getProperty('pid');
          if (empty($pid)) {
              return;
          }
          $filters = $this->connection
              ->createQueryBuilder()
              ->select('id', 'name')
              ->from('tl_metamodel_filter')
              ->where('pid=:id')
              ->setParameter('id', $model->getProperty('pid'))
              ->execute()
              ->fetchAll(\PDO::FETCH_ASSOC);
  
          $options = [];
          foreach ($filters as $filter) {
              $options[$filter['id']] = $filter['name'];
          }
  
          $event->setOptions($options);
      }
docs: Retrieve the options for the attributes.
  
  @param GetPropertyOptionsEvent $event The event.
  
  @return void