Braintree\PaymentMethodGateway::_validateId PHP Method

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