* UnsupportedOperationException}.
   *
   * <p>The default value is {@code false}.
   */
  @CanIgnoreReturnValue
  public ValueGraphBuilder<N, V> allowsSelfLoops(boolean allowsSelfLoops) {
    this.allowsSelfLoops = allowsSelfLoops;
    return this;
  }

  /**
   * Specifies the expected number of nodes in the graph.
   *

   * UnsupportedOperationException}.
   *
   * <p>The default value is {@code false}.
   */
  @CanIgnoreReturnValue
  public GraphBuilder<N> allowsSelfLoops(boolean allowsSelfLoops) {
    this.allowsSelfLoops = allowsSelfLoops;
    return this;
  }

  /**
   * Specifies the expected number of nodes in the graph.
   *

   */
  StandardValueGraph(
      AbstractGraphBuilder<? super N> builder,
      Map<N, GraphConnections<N, V>> nodeConnections,
      long edgeCount) {
    this.isDirected = builder.directed;
    this.allowsSelfLoops = builder.allowsSelfLoops;
    this.nodeOrder = builder.nodeOrder.cast();
    // Prefer the heavier "MapRetrievalCache" for nodes if lookup is expensive.
    this.nodeConnections =
        (nodeConnections instanceof TreeMap)

  }

  /** Returns a string representation of this graph. */
  @Override
  public String toString() {
    return "isDirected: "
        + isDirected()
        + ", allowsSelfLoops: "
        + allowsSelfLoops()
        + ", nodes: "
        + nodes()
        + ", edges: "
        + edges();
  }

   *     nodeV}, or null if there was no such edge.
   * @throws IllegalArgumentException if the introduction of the edge would violate {@link
   *     #allowsSelfLoops()}
   */
  @CanIgnoreReturnValue
  @Nullable V putEdgeValue(N nodeU, N nodeV, V value);

  /**
   * Adds an edge connecting {@code endpoints} if one is not already present, and sets a value for

   *
   * @return {@code true} if the graph was modified as a result of this call
   * @throws IllegalArgumentException if the introduction of the edge would violate {@link
   *     #allowsSelfLoops()}
   */
  @CanIgnoreReturnValue
  boolean putEdge(N nodeU, N nodeV);

  /**
   * Adds an edge connecting {@code endpoints} (in the order, if any, specified by {@code

     *
     * @return this {@code Builder} object
     * @throws IllegalArgumentException if the introduction of the edge would violate {@link
     *     #allowsSelfLoops()}
     */
    @CanIgnoreReturnValue
    public Builder<N> putEdge(N nodeU, N nodeV) {
      mutableGraph.putEdge(nodeU, nodeV);
      return this;
    }

    /**

/**
 * A base class for builders that construct graphs with user-defined properties.
 *
 * @author James Sexton
 */
abstract class AbstractGraphBuilder<N> {
  final boolean directed;
  boolean allowsSelfLoops = false;
  ElementOrder<N> nodeOrder = ElementOrder.insertion();
  ElementOrder<N> incidentEdgeOrder = ElementOrder.unordered();

  @Nullable Integer expectedNodeCount = null;

  /**

     *     connect {@code nodeU} to {@code nodeV}
     * @throws IllegalArgumentException if the introduction of the edge would violate {@link
     *     #allowsParallelEdges()} or {@link #allowsSelfLoops()}
     */
    @CanIgnoreReturnValue
    public ImmutableNetwork.Builder<N, E> addEdge(N nodeU, N nodeV, E edge) {
      mutableNetwork.addEdge(nodeU, nodeV, edge);
      return this;
    }

    /**

   * to add a self-loop to a graph that does not allow them will throw an {@link
   * IllegalArgumentException}.
   */
  boolean allowsSelfLoops();

  /** Returns the order of iteration for the elements of {@link #nodes()}. */
  ElementOrder<N> nodeOrder();

  //
  // Element-level accessors
  //

  /**