public function get_import_files($contextid) {
        global $USER;

        $fs = get_file_storage();
        $files = $fs->get_directory_files($contextid,
                                          'assignfeedback_file',
                                          ASSIGNFEEDBACK_FILE_IMPORT_FILEAREA,
                                          $USER->id,
                                          '/import/', true); // Get files recursive (all levels).

        $keys = array_keys($files);

        return $files;
    }