protected function notify(array $events)
    {
        $this->logger->debug(sprintf('POST notification to Recommendation Service: %s', json_encode($events, true)));

        $data = array(
            'json' => array(
                'transaction' => null,
                'events' => $events,
            ),
            'auth' => array(
                $this->options['customer-id'],
                $this->options['license-key'],
            ),
        );

        if (method_exists($this->guzzle, 'post')) {
            $this->notifyGuzzle5($data);
        } else {
            $this->notifyGuzzle6($data);
        }
    }