public function getAvailableLanguageCodes()
    {
        $cache = Cache::getTransientCache();
        $cacheId = 'transifex_languagescodes_' . $this->projectSlug;
        $languageCodes = $cache->fetch($cacheId);

        if (empty($languageCodes)) {
            $apiData = $this->getApiResults('project/' . $this->projectSlug . '/languages');
            foreach ($apiData as $languageData) {
                $languageCodes[] = $languageData->language_code;
            }
            $cache->save($cacheId, $languageCodes);
        }
        return $languageCodes;
    }