public function transformReadonly(FieldList $fields)
    {
        foreach ($fields->dataFields() as $field) {
            if ($field instanceof HiddenField) {
                continue;
            }
            $newField = $field->castedCopy(HTMLReadonlyField::class);
            $fields->replaceField($field->getName(), $newField);
        }
        return $fields;
    }