Dumplie\SharedKernel\Domain\Money\Currencies::isValid PHP Method

    public static function isValid(string $code) : bool
    {
        return array_key_exists(mb_strtoupper($code), self::$codes);
    }

 /**
  * @param CartId $cartId
  * @param string $currency
  *
  * @throws InvalidArgumentException
  */
 public function __construct(CartId $cartId, string $currency)
 {
     if (!Currencies::isValid($currency)) {
         throw InvalidArgumentException::invalidCurrency($currency);
     }
     $this->id = $cartId;
     $this->items = [];
     $this->currency = $currency;
 }