code: public function setValueOptionsMultiple(ManipulateWidgetEvent $event)
      {
          if (!$this->wantToHandle($event)) {
              return;
          }
  
          if ($event->getModel()->getProperty('type') !== 'conditionpropertycontainanyof') {
              return;
          }
  
          $metaModel = $this->getMetaModel($event->getEnvironment());
          $attribute = $metaModel->getAttributeById($event->getModel()->getProperty('attr_id'));
  
          if (!($attribute && ($attribute->get('type') == 'tags'))) {
              return;
          }
  
          $event->getWidget()->multiple = true;
      }
docs: Set the the value select to multiple.
  
  @param ManipulateWidgetEvent $event The event.
  
  @return void