abstract @Nullable N visitNext(Deque<Iterator<? extends N>> horizon);
  }

  /** Poor man's method reference for {@code Deque::addFirst} and {@code Deque::addLast}. */
  private enum InsertionOrder {
    FRONT {
      @Override
      <T> void insertInto(Deque<T> deque, T value) {
        deque.addFirst(value);
      }
    },
    BACK {
      @Override
      <T> void insertInto(Deque<T> deque, T value) {

        header.previous.remove();
        return last;
    }

    /**
     * Adds an element at the beginning.
     *
     * @param element the object to be added
     */
    public void addFirst(final E element) {
        header.next.addBefore(element);
    }

    /**
     * Adds an element at the end.
     *
     * @param element the object to be added
     */

        } else {
            return
        }

        typeTable['@role'] = 'dslTypes'
    }

    def mergeBlocks(Element blocksTable, DslDocModel model) {
        blocksTable.addFirst {
            thead {
                tr {
                    td('Block')
                    td('Description')
                }
            }
        }

            for (HtmlElementHandler handler : elementHandlers) {
                if (handler.onStartElement(name, attributes)) {
                    handlerStack.addFirst(handler);
                    tagStack.addFirst(name);
                    return;
                }
            }
            throw new UnsupportedOperationException();
        }

        @Override

          taskRunner.assertLockHeld()
          currentTask = self
          taskRunner.notifyAll()
        }
      }

    if (strategy == ResumePriority.BeforeOtherTasks) {
      serialTaskQueue.addFirst(yieldCompleteTask)
    } else {
      serialTaskQueue.addLast(yieldCompleteTask)
    }

    val startedTask = startNextTask()
    val otherTasksStarted = startedTask != yieldCompleteTask

    try {

  @CanIgnoreReturnValue
  @ParametricNullness
  public <C extends @Nullable Closeable> C register(@ParametricNullness C closeable) {
    if (closeable != null) {
      stack.addFirst(closeable);
    }

    return closeable;
  }

  /**
   * Stores the given throwable and rethrows it. It will be rethrown as is if it is an {@code

        }
    }

    /**
     * Initializes the {@link Logger}.
     */
    protected static synchronized void initialize() {
        DisposableUtil.addFirst(() -> {
            initialized = false;
            loggers.clear();
            factory.releaseAll();
        });
        initialized = true;
    }

    /**