private function getIndexFieldName(int $depth): string
    {
        if ($depth === 0) {
            return self::$fieldName;
        }

        return sprintf(self::$relatedContentFieldName, $depth);
    }
private function getIndexFieldName(int $depth): string
    {
        if ($depth === 0) {
            return self::$fieldName;
        }

        return sprintf(self::$relatedContentFieldName, $depth);
    }
Returns field name base on given depth.

@param int $depth

@return string