code: public function decodeValue(DecodePropertyValueForWidgetEvent $event)
      {
          if (!$this->wantToHandle($event)) {
              return;
          }
  
          if (is_array($event->getValue())) {
              $values = [];
  
              foreach ($event->getValue() as $value) {
                  $values[] = 'value_' . $value;
              }
  
              // Cut off the 'value_' prefix.
              $event->setValue($values);
          } else {
              $event->setValue('value_' . $event->getValue());
          }
      }
docs: Translates an value to a generated alias to allow numeric values.
  
  @param DecodePropertyValueForWidgetEvent $event The event.
  
  @return void