public function refresh_files() {
        $converter = new \core_files\converter();
        foreach ($this->sourcefiles as $file) {
            if (is_a($file, \core_files\conversion::class)) {
                $status = $file->get('status');
                switch ($status) {
                    case \core_files\conversion::STATUS_COMPLETE:
                        continue 2;
                        break;
                    default:
                        $converter->poll_conversion($conversion);
                }
            }
        }

        return $this;
    }