sink: MutableCollection<in T>,
      maxElements: Int,
    ) = error("unsupported")
  }

  /** Returns true if no tasks have been scheduled. This runs the coordinator for confirmation. */
  fun isIdle() = taskRunner.activeQueues().isEmpty()

  override fun close() {
    tasksExecutor.shutdownNow()
  }

  companion object {
    var instance = 0

    @JvmField