public static function displayName($propertyName) {
        $propertyName = (is_array($propertyName) ? implode('_', $propertyName) : $propertyName);

        if (($dataAnnotation = self::$viewContext->getModelDataAnnotation($propertyName)) !== null) {
            return htmlspecialchars($dataAnnotation->displayName);
        }
        else {
            return '';
        }
    }