* equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}, and to
   * {@code edgeConnectingOrNull(nodeU, nodeV) != null}.
   *
   * <p>In an undirected network, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}.
   *
   * @since 23.0
   */
  boolean hasEdgeConnecting(N nodeU, N nodeV);

  /**

   */
  @CanIgnoreReturnValue
  boolean addNode(N node);

  /**
   * Adds an edge connecting {@code nodeU} to {@code nodeV} if one is not already present.
   *
   * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
   * undirected.
   *
   * <p>If {@code nodeU} and {@code nodeV} are not already present in this graph, this method will

    checkArgument(containsNode(nodeV), NODE_NOT_IN_GRAPH, nodeV);
    return nodePairInvalidatableSet(connectionsU.edgesConnecting(nodeV), nodeU, nodeV);
  }

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

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

  @Override

   *
   * <p>If {@code nodeU} and {@code nodeV} are not already present in this graph, this method will
   * silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the graph.
   *
   * <p>If {@code edge} already connects {@code nodeU} to {@code nodeV} (in the specified order if
   * this network {@link #isDirected()}, else in any order), then this method will have no effect.
   *

  public boolean removeNode(N node) {
    return backingValueGraph.removeNode(node);
  }

  @Override
  public boolean removeEdge(N nodeU, N nodeV) {
    return backingValueGraph.removeEdge(nodeU, nodeV) != null;
  }

  @Override
  public boolean removeEdge(EndpointPair<N> endpoints) {
    validateEndpoints(endpoints);
    return removeEdge(endpoints.nodeU(), endpoints.nodeV());
  }

  @Override
  public int degree(N node) {
    return delegate().degree(node);
  }

  @Override
  public int inDegree(N node) {
    return delegate().inDegree(node);
  }

  @Override
  public int outDegree(N node) {
    return delegate().outDegree(node);
  }

  @Override
  public boolean hasEdgeConnecting(N nodeU, N nodeV) {
    return delegate().hasEdgeConnecting(nodeU, nodeV);
  }

  @Override

      return (node.equals(source) && graph.successors(node).contains(target))
          || (node.equals(target) && graph.predecessors(node).contains(source));
    } else {
      if (endpointPair.isOrdered()) {
        return false;
      }
      Set<N> adjacent = graph.adjacentNodes(node);
      Object nodeU = endpointPair.nodeU();
      Object nodeV = endpointPair.nodeV();

    // whatever ordering the graph's nodes do, so ImmutableSortedMap is unnecessary even if the
    // input nodes are sorted.
    ImmutableMap.Builder<N, GraphConnections<N, V>> nodeConnections = ImmutableMap.builder();
    for (N node : graph.nodes()) {
      nodeConnections.put(node, connectionsOf(graph, node));
    }
    return nodeConnections.buildOrThrow();
  }

   * Returns true if there is an edge that directly connects {@code nodeU} to {@code nodeV}. This is
   * equivalent to {@code nodes().contains(nodeU) && successors(nodeU).contains(nodeV)}.
   *
   * <p>In an undirected graph, this is equal to {@code hasEdgeConnecting(nodeV, nodeU)}.
   *
   * @since 23.0
   */
  boolean hasEdgeConnecting(N nodeU, N nodeV);

  /**

      assertThat(network.adjacentNodes(nodeU)).contains(nodeV);
      assertThat(network.outEdges(nodeU)).contains(edge);
      assertThat(network.incidentEdges(nodeU)).contains(edge);
      assertThat(network.predecessors(nodeV)).contains(nodeU);
      assertThat(network.adjacentNodes(nodeV)).contains(nodeU);
      assertThat(network.inEdges(nodeV)).contains(edge);
      assertThat(network.incidentEdges(nodeV)).contains(edge);