public function getFileRelationClassName($gridField)
    {
        $recordClass = $this->getRecordClassName($gridField);
        $hasOneFields = Config::inst()->get($recordClass, 'has_one');

        $fieldName = $this->getFileRelationName($gridField);
        if ($fieldName) {
            return $hasOneFields[$fieldName];
        } else {
            return 'SilverStripe\\Assets\\File';
        }
    }