private function getLanguages()
    {
        $allLanguages = $this->manager->languages();

        if (! $this->option('lang')) {
            return $allLanguages;
        }

        $userLanguages = explode(',', (string) $this->option('lang'));

        if ($missingLanguages = array_diff($userLanguages, $allLanguages)) {
            throw new InvalidArgumentException('Unknown Language(s) ['.implode(',', $missingLanguages).'].');
        }

        return $userLanguages;
    }