public function getTimestamp(): ?int
    {
        $value = $this->getHeader('timestamp');

        return null === $value ? null : (int) $value;
    }

    public function getTimestamp(): ?int
    {
            $attributes = $message->getAttributes();
            if (isset($attributes['SentTimestamp'])) {
                $sentTimestamp = (int) $attributes['SentTimestamp'];
                if ($sentTimestamp > 0) {
                    // SQS SentTimestamp is milliseconds since epoch.
                    return intdiv($sentTimestamp, 1000);
                }
            }
            return null;
    }