//                                                                           =========
    private static final DataConfigDbm _instance = new DataConfigDbm();

    private DataConfigDbm() {
    }

    public static DataConfigDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final RelatedContentDbm _instance = new RelatedContentDbm();

    private RelatedContentDbm() {
    }

    public static RelatedContentDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final ScheduledJobDbm _instance = new ScheduledJobDbm();

    private ScheduledJobDbm() {
    }

    public static ScheduledJobDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final KeyMatchDbm _instance = new KeyMatchDbm();

    private KeyMatchDbm() {
    }

    public static KeyMatchDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final FileAuthenticationDbm _instance = new FileAuthenticationDbm();

    private FileAuthenticationDbm() {
    }

    public static FileAuthenticationDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

  private final Stats yStats;
  private final double sumOfProductsOfDeltas;

  /**
   * Internal constructor. Users should use {@link PairedStatsAccumulator#snapshot}.
   *
   * <p>To ensure that the created instance obeys its contract, the parameters should satisfy the
   * following constraints. This is the callers responsibility and is not enforced here.
   *
   * <ul>

    //                                                                           =========
    private static final ClickLogDbm _instance = new ClickLogDbm();

    private ClickLogDbm() {
    }

    public static ClickLogDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final ElevateWordDbm _instance = new ElevateWordDbm();

    private ElevateWordDbm() {
    }

    public static ElevateWordDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final JobLogDbm _instance = new JobLogDbm();

    private JobLogDbm() {
    }

    public static JobLogDbm getInstance() {
        return _instance;
    }

    // ===================================================================================

    //                                                                           =========
    private static final PathMappingDbm _instance = new PathMappingDbm();

    private PathMappingDbm() {
    }

    public static PathMappingDbm getInstance() {
        return _instance;
    }

    // ===================================================================================