* comment: Target files for index backup.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexBackupTargets();

    /**
     * Get the value for the key 'index.backup.log.targets'. <br>
     * The value is, e.g. click_log.ndjson,favorite_log.ndjson,search_log.ndjson,user_info.ndjson <br>