private function unmapTopic($topic)
    {
        if (array_key_exists($topic, self::ID_TO_TOPIC_ENUM)) {
            $result = self::ID_TO_TOPIC_ENUM[$topic];
            $this->logger->debug(sprintf('Topic ID "%s" has been unmapped to "%s".', $topic, $result));
        } else {
            $result = $topic;
            $this->logger->debug(sprintf('Topic ID "%s" does not exist in enum.', $topic));
        }

        return $result;
    }