/**
     * Adds a URL to the queue.
     *
     * @param sessionId The session ID.
     * @param url The URL.
     */
    void add(String sessionId, String url);

    /**
     * Inserts a URL queue.
     *
     * @param urlQueue The URL queue.
     */
    void insert(QUEUE urlQueue);

    /**
     * Deletes a URL queue.
     *
     * @param sessionId The session ID.
     */

    ListenerCallQueue<Object> queue = new ListenerCallQueue<>();
    queue.addListener(listener, directExecutor());

    Multiset<Object> counters = ConcurrentHashMultiset.create();
    queue.enqueue(incrementingEvent(counters, listener, 1));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 2));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 3));

    ListenerCallQueue<Object> queue = new ListenerCallQueue<>();
    queue.addListener(listener, directExecutor());

    Multiset<Object> counters = ConcurrentHashMultiset.create();
    queue.enqueue(incrementingEvent(counters, listener, 1));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 2));
    queue.enqueue(THROWING_EVENT);
    queue.enqueue(incrementingEvent(counters, listener, 3));

     */
    public synchronized void addUrlQueueList(final String sessionId, final Queue<UrlQueueImpl<Long>> urlQueueList) {
        final Queue<UrlQueueImpl<Long>> uqList = getUrlQueueList(sessionId);
        uqList.addAll(urlQueueList);
        urlQueueMap.put(sessionId, uqList);
    }

    /**
     * Removes the URL queue for the specified session ID.
     * @param sessionId the session ID
     */

  }

  private void enqueueHelper(Event<L> event, Object label) {
    checkNotNull(event, "event");
    checkNotNull(label, "label");
    synchronized (listeners) {
      for (PerListenerQueue<L> queue : listeners) {
        queue.add(event, label);
      }
    }
  }

  /**
   * Dispatches all events enqueued prior to this call, serially and in order, for every listener.
   *

//
// `tensor` is still owned by the caller. This call will be blocked if the queue
// has reached its capacity, and will be unblocked when the queued tensors again
// drop below the capacity due to dequeuing.
//
// Tensors are dequeued via the corresponding TF dequeue op.
// TODO(hongm): Add support for `timeout_ms`.
TF_CAPI_EXPORT extern void TF_EnqueueNamedTensor(TF_Session* session,

    /** Runnable is not running and not queued for execution */
    IDLE,
    /** Runnable is not running, but is being queued for execution */
    QUEUING,
    /** runnable has been submitted but has not yet begun execution */
    QUEUED,
    RUNNING,
  }

  /** Underlying executor that all submitted Runnable objects are run on. */
  private final Executor executor;

  @GuardedBy("queue")

    /** Runnable is not running and not queued for execution */
    IDLE,
    /** Runnable is not running, but is being queued for execution */
    QUEUING,
    /** runnable has been submitted but has not yet begun execution */
    QUEUED,
    RUNNING,
  }

  /** Underlying executor that all submitted Runnable objects are run on. */
  private final Executor executor;

  @GuardedBy("queue")

    task.nextExecuteNanoTime = -1L
    val queue = task.queue!!
    queue.futureTasks.remove(task)
    readyQueues.remove(queue)
    queue.activeTask = task
    busyQueues.add(queue)
  }

  private fun afterRun(
    task: Task,
    delayNanos: Long,
    completedNormally: Boolean,
  ) {
    assertLockHeld()

    val queue = task.queue!!
    check(queue.activeTask === task)

 *   <li>Deleting URL queues associated with a session.</li>
 *   <li>Deleting all URL queues.</li>
 *   <li>Offering a list of URLs to the queue, ensuring duplicates are not added.</li>
 *   <li>Polling (retrieving and removing) a URL from the queue.</li>
 *   <li>Saving the session (currently a no-op).</li>
 *   <li>Checking if a URL has already been visited.</li>
 *   <li>Generating URL queues from a previous session's access results.</li>