public function getGateway()
    {
        /* @var $module \gplcart\modules\omnipay_library\Main */
        $module = $this->module->getInstance('omnipay_library');

        /** @var \Omnipay\Stripe\Gateway $gateway */
        $gateway = $module->getGatewayInstance('Stripe');

        if (!$gateway instanceof Gateway) {
            throw new UnexpectedValueException('Gateway must be instance of Omnipay\Stripe\Gateway');
        }

        return $gateway;
    }