public function getAuth($errorOnNull = false)
    {
        if ($errorOnNull && !$this->auth) {
            $msg = 'No Auth object provided.  (HINT: Set your Auth data using '
                 . '"$API->setAuth(Auth $auth)" or $API\' constructor.  '
                 . 'See https://TODO for details.';
            throw new ApiException($msg);
        }

        return $this->auth;
    }