public static function siretToSiren($siret, bool $format = false): string
    {
        $value = (string) (int) $siret;
        if (!self::isSiret($value)) {
            return '';
        }
        return $format 
             ? preg_replace('/^([0-9]{3})([0-9]{3})([0-9]{3})([0-9]{5})$/', '$1 $2 $3', $value)
             : substr($value, 0, 9);
    }