private function count_files($submissionid, $area) {
        $fs = get_file_storage();
        $files = $fs->get_area_files($this->assignment->get_context()->id,
                                     'assignsubmission_file',
                                     $area,
                                     $submissionid,
                                     'id',
                                     false);

        return count($files);
    }