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

    private WebAuthenticationDbm() {
    }

    public static WebAuthenticationDbm getInstance() {
        return _instance;
    }

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

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

    private ElevateWordDbm() {
    }

    public static ElevateWordDbm getInstance() {
        return _instance;
    }

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

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

    private ClickLogDbm() {
    }

    public static ClickLogDbm getInstance() {
        return _instance;
    }

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

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

    private DataConfigDbm() {
    }

    public static DataConfigDbm getInstance() {
        return _instance;
    }

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

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

    private AccessTokenDbm() {
    }

    public static AccessTokenDbm 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 ScheduledJobDbm _instance = new ScheduledJobDbm();

    private ScheduledJobDbm() {
    }

    public static ScheduledJobDbm getInstance() {
        return _instance;
    }

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

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

    private FileConfigDbm() {
    }

    public static FileConfigDbm getInstance() {
        return _instance;
    }

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

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

    private WebConfigDbm() {
    }

    public static WebConfigDbm getInstance() {
        return _instance;
    }

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

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

    private SearchLogDbm() {
    }

    public static SearchLogDbm getInstance() {
        return _instance;
    }

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