class UserBackupManagerService {

    public long getAncestralSerialNumber() {
        // TODO (b/124359804)
        try (RandomAccessFile af = getAncestralSerialNumberFile()) {
            return af.readLong();
        } catch (IOException e) {
            Slog.w(TAG, "Unable to write to work profile serial number file:", e);
            return -1;
        }
    }

    private  UserBackupManagerService(
            @UserIdInt int userId,
            Context context,
            Trampoline parent,
            HandlerThread userBackupThread,
            File baseStateDir,
            File dataDir,
            TransportManager transportManager);

}