@Override
  public Set<N> predecessors() {
    return Collections.unmodifiableSet(predecessorsMultiset().elementSet());
  }

  private Multiset<N> predecessorsMultiset() {
    Multiset<N> predecessors = getReference(predecessorsReference);
    if (predecessors == null) {
      predecessors = HashMultiset.create(inEdgeMap.values());

 * which has a method {@code getParents()} that retrieves its predecessors in a graph:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, MyNode::getParents);
 * }
 *
 * <p>If you have some other mechanism for returning the predecessors of a node, or one that doesn't
 * return a {@code Iterable<? extends N>}, then you can use a lambda to perform a more general

  /** Remove {@code node} from the set of predecessors. */
  void removePredecessor(N node);

  /**
   * Remove {@code node} from the set of successors. Returns the value previously associated with
   * the edge connecting the two nodes.
   */
  @CanIgnoreReturnValue
  @Nullable V removeSuccessor(N node);

  /**
   * Add {@code node} as a predecessor to the origin node. In the case of an undirected graph, it

                      Iterators.transform(
                          graph.predecessors(node).iterator(),
                          (N predecessor) -> EndpointPair.ordered(predecessor, node)),
                      Iterators.transform(
                          // filter out 'node' from successors (already covered by predecessors,
                          // above)

    return delegate().incidentEdgeOrder();
  }

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public int degree(N node) {

    return delegate().edgeOrder();
  }

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<E> incidentEdges(N node) {

  //
  // 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)}.
   *
   * <p>If {@code node} is removed from the graph after this method is called, the {@code Set}
   * {@code view} returned by this method will be invalidated, and will throw {@code

    return delegate().incidentEdgeOrder();
  }

  @Override
  public Set<N> adjacentNodes(N node) {
    return delegate().adjacentNodes(node);
  }

  @Override
  public Set<N> predecessors(N node) {
    return delegate().predecessors(node);
  }

  @Override
  public Set<N> successors(N node) {
    return delegate().successors(node);
  }

  @Override
  public Set<EndpointPair<N>> incidentEdges(N node) {

    }

    @Override
    Graph<N> delegate() {
      return graph;
    }

    @Override
    public Set<N> predecessors(N node) {
      return delegate().successors(node); // transpose
    }

    @Override
    public Set<N> successors(N node) {
      return delegate().predecessors(node); // transpose
    }

    @Override
    public Set<EndpointPair<N>> incidentEdges(N node) {

                        })
                        .orElse(false);

                // Check if any predecessor failed - if so, we'll run the step but mark it as SKIPPED
                boolean anyPredecessorFailed = step.predecessors.stream().anyMatch(s -> s.status.get() == FAILED);

                // If any predecessor failed, we'll use a special status transition: CREATED -> SKIPPED