while (resultWithDoubleSelfLoop.hasNext()) {
          EndpointPair<N> edge = resultWithDoubleSelfLoop.next();
          if (edge.nodeU().equals(edge.nodeV())) {
            if (!alreadySeenSelfLoop.getAndSet(true)) {
              return edge;
            }
          } else {
            return edge;
          }
        }
        return endOfData();
      }
    };
  }

     * cancelled before the callable started execution.
     */
    SettableFuture<@Nullable Void> newFuture = SettableFuture.create();

    ListenableFuture<@Nullable Void> oldFuture = ref.getAndSet(newFuture);

    // Invoke our task once the previous future completes.
    TrustedListenableFutureTask<T> taskFuture = TrustedListenableFutureTask.create(task);
    oldFuture.addListener(taskFuture, taskExecutor);

     * cancelled before the callable started execution.
     */
    SettableFuture<@Nullable Void> newFuture = SettableFuture.create();

    ListenableFuture<@Nullable Void> oldFuture = ref.getAndSet(newFuture);

    // Invoke our task once the previous future completes.
    TrustedListenableFutureTask<T> taskFuture = TrustedListenableFutureTask.create(task);
    oldFuture.addListener(taskFuture, taskExecutor);

   *
   * <p>Triggers test case failure if interrupt status is set in the main thread.
   */
  @Override
  public void tearDown() throws Exception {
    Throwable t = threadFailure.getAndSet(null);
    if (t != null) {
      if (t instanceof Error) throw (Error) t;
      else if (t instanceof RuntimeException) throw (RuntimeException) t;
      else if (t instanceof Exception) throw (Exception) t;