private final Object mutex = new Object[0]; // something Serializable

    @Override
    public boolean offer(E o) {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.offer(o);
    }

    @Override
    public @Nullable E poll() {
      assertTrue(Thread.holdsLock(mutex));
      return delegate.poll();
    }

    @Override
    public E remove() {
      assertTrue(Thread.holdsLock(mutex));

  }

  @Override
  boolean isPartialView() {
    return false;
  }

  @Override
  public C first() {
    // requireNonNull is safe because we checked the range is not empty in ContiguousSet.create.
    return requireNonNull(range.lowerBound.leastValueAbove(domain));
  }

  @Override
  public C last() {

        int attributes;

        @Override
        public int getAttributes() {
            return attributes;
        }

        @Override
        public long getCreateTime() {
            return createTime;
        }

        @Override
        public long getLastWriteTime() {
            return lastWriteTime;
        }

        @Override
        public long getSize() {
            return 0L;

    @Override
    public String getProjectName() {
        return null;
    }

    @Override
    public String getProjectPrefix() {
        return null;
    }

    @Override
    public String getGenerationGapBasePrefix() {
        return null;
    }

    @Override
    public DBDef getCurrentDBDef() {
        return null;
    }

    @Override
    public String getProjectName() {
        return null;
    }

    @Override
    public String getProjectPrefix() {
        return null;
    }

    @Override
    public String getGenerationGapBasePrefix() {
        return null;
    }

    @Override
    public DBDef getCurrentDBDef() {
        return null;
    }

    @Override
    public String getProjectName() {
        return null;
    }

    @Override
    public String getProjectPrefix() {
        return null;
    }

    @Override
    public String getGenerationGapBasePrefix() {
        return null;
    }

    @Override
    public DBDef getCurrentDBDef() {
        return null;
    }

    }

    @Override
    String getKeyRole() {
      return "Column";
    }

    @Override
    Map<R, @Nullable V> getValue(int index) {
      return new Column(index);
    }

    @Override
    Map<R, @Nullable V> setValue(int index, Map<R, @Nullable V> newValue) {
      throw new UnsupportedOperationException();
    }

    @Override

        TODO("Can't get here")
      }
    }

    override fun put(element: T) {
      taskRunner.withLock {
        delegate.put(element)
        editCount++
      }
    }

    override fun iterator() = error("unsupported")

    override fun offer(e: T) = error("unsupported")

    override fun peek(): T = error("unsupported")

    override fun offer(
      element: T,
      timeout: Long,

      this.backingSet = backingSet;
    }

    @Override
    protected Set<T> delegate() {
      return backingSet;
    }

    @Override
    public boolean equals(@Nullable Object object) {
      return standardEquals(object);
    }

    @Override
    public int hashCode() {
      return standardHashCode();
    }

    @Override
    public boolean addAll(Collection<? extends T> collection) {

  }

  @Override
  public String toString() {
    return serviceName() + " [" + state() + "]";
  }

  @Override
  public final boolean isRunning() {
    return delegate.isRunning();
  }

  @Override
  public final State state() {
    return delegate.state();
  }

  /**
   * @since 13.0
   */
  @Override