@CanIgnoreReturnValue
  N removeOutEdge(E edge);

  /**
   * Add {@code edge} to the set of incoming edges. Implicitly adds {@code node} as a predecessor.
   */
  void addInEdge(E edge, N node, boolean isSelfLoop);

  /** Add {@code edge} to the set of outgoing edges. Implicitly adds {@code node} as a successor. */
  void addOutEdge(E edge, N node);

      Object target = endpointPair.target();
      return (node.equals(source) && successorsOrEmpty(node).contains(target))
          || (node.equals(target) && predecessorsOrEmpty(node).contains(source));
    } else {
      Set<N> adjacent = graph.adjacentNodes(node);
      Object nodeU = endpointPair.nodeU();
      Object nodeV = endpointPair.nodeV();

      return (node.equals(nodeV) && adjacent.contains(nodeU))

  @Override
  @CanIgnoreReturnValue
  public boolean addNode(N node) {
    checkNotNull(node, "node");

    if (containsNode(node)) {
      return false;
    }

    addNodeInternal(node);
    return true;
  }

  /**
   * Adds {@code node} to the graph and returns the associated {@link NetworkConnections}.
   *
   * @throws IllegalStateException if {@code node} is already present
   */
  @CanIgnoreReturnValue

  }

  @Override
  public int degree(N node) {
    if (isDirected()) {
      return IntMath.saturatedAdd(inEdges(node).size(), outEdges(node).size());
    } else {
      return IntMath.saturatedAdd(incidentEdges(node).size(), edgesConnecting(node, node).size());
    }
  }

  @Override
  public int inDegree(N node) {
    return isDirected() ? inEdges(node).size() : degree(node);
  }

  @Override

  }

  @Override
  public int degree(N node) {
    if (isDirected()) {
      return IntMath.saturatedAdd(inEdges(node).size(), outEdges(node).size());
    } else {
      return IntMath.saturatedAdd(incidentEdges(node).size(), edgesConnecting(node, node).size());
    }
  }

  @Override
  public int inDegree(N node) {
    return isDirected() ? inEdges(node).size() : degree(node);
  }

  @Override

  }

  @Override
  public @Nullable V value(N node) {
    return adjacentNodeValues.get(node);
  }

  @Override
  public void removePredecessor(N node) {
    @SuppressWarnings("unused")
    V unused = removeSuccessor(node);
  }

  @Override
  public @Nullable V removeSuccessor(N node) {
    return adjacentNodeValues.remove(node);
  }

  @Override

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

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

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

      @Override

  }

  @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) {
    return delegate().incidentEdges(node);
  }

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

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

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

  @Override

  }

  @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) {
    return delegate().incidentEdges(node);
  }