public static function get_extra_config($class, $extension, $args)
    {
        if (!self::is_translatable_installed()) {
            // remain silent during a test
            if (SapphireTest::is_running_test()) {
                return null;
            }
            // raise an error otherwise
            user_error('Translatable module is not installed but required.', E_USER_WARNING);
            return null;
        }

        if ($args) {
            self::$arguments[$class] = $args;
        }

        return array(
            'db' => self::collectDBFields($class),
            'has_one' => self::collectHasOneRelations($class)
        );
    }