}

      for (N successor : sanityCheckSet(network.successors(node))) {
        assertThat(network.predecessors(successor)).contains(node);
        assertThat(network.edgesConnecting(node, successor)).isNotEmpty();
      }

      for (E incidentEdge : sanityCheckSet(network.incidentEdges(node))) {
        assertTrue(
            network.inEdges(node).contains(incidentEdge)

  }

  private static final class NodeAndRemainingSuccessors<N> {
    final N node;

    /**
     * The successors left to be visited, or {@code null} if we just added this {@code
     * NodeAndRemainingSuccessors} instance to the stack. In the latter case, we'll compute the
     * successors if we determine that we need them after we've performed the initial processing of
     * the node.
     */

  }

  private static final class NodeAndRemainingSuccessors<N> {
    final N node;

    /**
     * The successors left to be visited, or {@code null} if we just added this {@code
     * NodeAndRemainingSuccessors} instance to the stack. In the latter case, we'll compute the
     * successors if we determine that we need them after we've performed the initial processing of
     * the node.
     */

    public Iterable<? extends Character> successors(Character node) {
      requestedNodes.add(node);
      return delegate.successors(node);
    }
  }

  private static <N> SuccessorsFunction<N> fixedSuccessors(Iterable<N> successors) {
    return new SuccessorsFunction<N>() {
      @Override
      public Iterable<N> successors(N n) {
        return successors;
      }
    };
  }

    public Iterable<? extends Character> successors(Character node) {
      requestedNodes.add(node);
      return delegate.successors(node);
    }
  }

  private static <N> SuccessorsFunction<N> fixedSuccessors(Iterable<N> successors) {
    return new SuccessorsFunction<N>() {
      @Override
      public Iterable<N> successors(N n) {
        return successors;
      }
    };
  }

    return new CompactLinkedHashSet<>(expectedSize);
  }

  private static final int ENDPOINT = -2;

  // TODO(user): predecessors and successors should be collocated (reducing cache misses).
  // Might also explore collocating all of [hash, next, predecessor, successor] fields of an
  // entry in a *single* long[], though that reduces the maximum size of the set by a factor of 2

  /**

  ElementOrder<E> edgeOrder();

  //
  // Element-level accessors
  //

  /**
   * Returns a live view of the nodes which have an incident edge in common with {@code node} in
   * this graph.
   *
   * <p>This is equal to the union of {@link #predecessors(Object)} and {@link #successors(Object)}.
   *

        if (current == State.HALF_OPEN) {
            int successes = halfOpenSuccesses.incrementAndGet();
            if (successes >= successThreshold) {
                if (state.compareAndSet(State.HALF_OPEN, State.CLOSED)) {
                    stateChangeTime.set(System.currentTimeMillis());
                    log.info("Circuit breaker {} closed after {} successful attempts", name, successes);
                }
            }
        }

        if (currentState == State.HALF_OPEN) {
            int successes = successCount.incrementAndGet();
            log.debug("[{}] Success in HALF_OPEN state ({}/{})", name, successes, successThreshold);

            if (successes >= successThreshold) {
                log.info("[{}] Circuit breaker closing after {} successful attempts", name, successes);
                transitionTo(State.CLOSED);
            }

    }
  }

  private static <T extends @Nullable Object> void successor(AvlNode<T> a, AvlNode<T> b) {
    a.succ = b;
    b.pred = a;
  }

  private static <T extends @Nullable Object> void successor(
      AvlNode<T> a, AvlNode<T> b, AvlNode<T> c) {
    successor(a, b);
    successor(b, c);
  }

  /*