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());
        }
    }