Braintree\CreditCardGateway::_validateId PHP Method

    private function _validateId($identifier = null, $identifierType = "token")
    {
        if (empty($identifier)) {
            throw new InvalidArgumentException('expected credit card id to be set');
        }
        if (!preg_match('/^[0-9A-Za-z_-]+$/', $identifier)) {
            throw new InvalidArgumentException($identifier . ' is an invalid credit card ' . $identifierType . '.');
        }
    }