protected function format(ItemFieldInterface $field, ItemInterface $item)
    {
        $class = get_class($field);

        switch ($class) {
            case GroupItemField::class:
                return $this->formatGroupItemField($field, $item);
                break;

            case MediaItemField::class:
                return $this->formatMediaItemField($field, $item);
                break;

            case ItemField::class:
                return $this->formatItemField($field, $item);
                break;
        }
    }