PARALLEL_EDGES_NOT_ALLOWED,
          nodeU,
          nodeV);
    }
    boolean isSelfLoop = nodeU.equals(nodeV);
    if (!allowsSelfLoops()) {
      checkArgument(!isSelfLoop, SELF_LOOPS_NOT_ALLOWED, nodeU);
    }

    if (connectionsU == null) {
      connectionsU = addNodeInternal(nodeU);
    }
    connectionsU.addOutEdge(edge, nodeV);

      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))

     *
     * <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
     * silently {@link #addNode(Object) add} {@code nodeU} and {@code nodeV} to the graph.
     *
     * @return this {@code Builder} object

    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

    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

    // 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();
  }

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

  /**
   * Returns true if there is an edge that directly connects {@code endpoints} (in the order, if

   * 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.
   *
   * @return {@code true} if the network was modified as a result of this call

  @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

  @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