addEdge(N1, N2, E12);
    Set<Integer> n1AdjacentNodes = network.adjacentNodes(N1);
    Set<Integer> n2AdjacentNodes = network.adjacentNodes(N2);
    Set<Integer> n1Predecessors = network.predecessors(N1);
    Set<Integer> n2Predecessors = network.predecessors(N2);
    Set<Integer> n1Successors = network.successors(N1);
    Set<Integer> n2Successors = network.successors(N2);
    Set<String> n1IncidentEdges = network.incidentEdges(N1);

 * 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

  }

  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

  /**
   * Pointer to the predecessor of an entry in insertion order. ENDPOINT indicates a node is the

    }

    @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) {

    }

    @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) {

 * transformation:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, node -> ImmutableList.of(node.leftChild(), node.rightChild()));
 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and
 * successors, iterating over the edges, etc.) should declare their input to be of a type that
 * provides those capabilities, such as {@link Graph}, {@link ValueGraph}, or {@link Network}.
 *

 * transformation:
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, node -> ImmutableList.of(node.leftChild(), node.rightChild()));
 * }
 *
 * <p>Graph algorithms that need additional capabilities (accessing both predecessors and
 * successors, iterating over the edges, etc.) should declare their input to be of a type that
 * provides those capabilities, such as {@link Graph}, {@link ValueGraph}, or {@link Network}.
 *

    return newBuilder;
  }

  /**
   * Specifies the order of iteration for the elements of {@link ValueGraph#edges()}, {@link
   * ValueGraph#adjacentNodes(Object)}, {@link ValueGraph#predecessors(Object)}, {@link
   * ValueGraph#successors(Object)} and {@link ValueGraph#incidentEdges(Object)}.
   *
   * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For

  // 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 network after this method is called, the {@code Set}

    return newBuilder;
  }

  /**
   * Specifies the order of iteration for the elements of {@link Graph#edges()}, {@link
   * Graph#adjacentNodes(Object)}, {@link Graph#predecessors(Object)}, {@link
   * Graph#successors(Object)} and {@link Graph#incidentEdges(Object)}.
   *
   * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For