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

    private RoleDbm() {
    }

    public static RoleDbm getInstance() {
        return _instance;
    }

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

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

    private ElevateWordToLabelDbm() {
    }

    public static ElevateWordToLabelDbm getInstance() {
        return _instance;
    }

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

  public String toString() {
    return super.toString();
  }

  private static boolean isProxyOfSameInterfaces(Object arg, Class<?> proxyClass) {
    return proxyClass.isInstance(arg)
        // Equal proxy instances should mostly be instance of proxyClass
        // Under some edge cases (such as the proxy of JDK types serialized and then deserialized)
        // the proxy type may not be the same.

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

    private UserInfoDbm() {
    }

    public static UserInfoDbm getInstance() {
        return _instance;
    }

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

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

    private CrawlingInfoDbm() {
    }

    public static CrawlingInfoDbm getInstance() {
        return _instance;
    }

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

  public String toString() {
    return super.toString();
  }

  private static boolean isProxyOfSameInterfaces(Object arg, Class<?> proxyClass) {
    return proxyClass.isInstance(arg)
        // Equal proxy instances should mostly be instance of proxyClass
        // Under some edge cases (such as the proxy of JDK types serialized and then deserialized)
        // the proxy type may not be the same.

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

    private FavoriteLogDbm() {
    }

    public static FavoriteLogDbm getInstance() {
        return _instance;
    }

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

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

    private GroupDbm() {
    }

    public static GroupDbm getInstance() {
        return _instance;
    }

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

   */
  fun <T : ConnectionEvent> removeUpToEvent(eventClass: Class<T>): T {
    val fullEventSequence = eventSequence.toList()
    try {
      while (true) {
        val event = takeEvent()
        if (eventClass.isInstance(event)) {
          return eventClass.cast(event)
        }
      }
    } catch (e: NoSuchElementException) {
      throw AssertionError("full event sequence: $fullEventSequence", e)
    }
  }

  /**

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

    private CrawlingInfoParamDbm() {
    }

    public static CrawlingInfoParamDbm getInstance() {
        return _instance;
    }

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