* properties remain intact, and further updates to {@code graph} will be reflected in the view.
   */
  public static <N> Graph<N> transpose(Graph<N> graph) {
    if (!graph.isDirected()) {
      return graph; // the transpose of an undirected graph is an identical graph
    }

    if (graph instanceof TransposedGraph) {
      return ((TransposedGraph<N>) graph).graph;

  private ImmutableValueGraph(ValueGraph<N, V> graph) {
    super(ValueGraphBuilder.from(graph), getNodeConnections(graph), graph.edges().size());
  }

  /** Returns an immutable copy of {@code graph}. */
  public static <N, V> ImmutableValueGraph<N, V> copyOf(ValueGraph<N, V> graph) {
    return (graph instanceof ImmutableValueGraph)
        ? (ImmutableValueGraph<N, V>) graph
        : new ImmutableValueGraph<N, V>(graph);
  }

  /** Constructor for use by subclasses. */
  public AbstractGraph() {}

  @Override
  public final boolean equals(@Nullable Object obj) {
    if (obj == this) {
      return true;
    }
    if (!(obj instanceof Graph)) {
      return false;
    }
    Graph<?> other = (Graph<?>) obj;

    return isDirected() == other.isDirected()
        && nodes().equals(other.nodes())

 */

package com.google.common.graph;

import java.util.Set;

/**
 * A non-public interface for the methods shared between {@link Graph} and {@link ValueGraph}.
 *
 * @author James Sexton
 * @param <N> Node parameter type
 */
interface BaseGraph<N> extends ArchetypeGraph<N> {
  //
  // Graph-level accessors
  //

  /** Returns all edges in this graph. */
  Set<EndpointPair<N>> edges();

  /**

   *
   * <p>If the graph is directed, the resultant edge will be directed; otherwise, it will be
   * undirected.
   *
   * <p>If this graph is directed, {@code endpoints} must be ordered.
   *
   * <p>Values do not have to be unique. However, values must be non-null.
   *
   * <p>If either or both endpoints are not already present in this graph, this method will silently

 *
 * <h3>Usage</h3>
 *
 * Given an algorithm, for example:
 *
 * {@snippet :
 * public <N> someGraphAlgorithm(N startNode, SuccessorsFunction<N> successorsFunction);
 * }
 *
 * you will invoke it depending on the graph representation you're using.
 *
 * <p>If you have an instance of one of the primary {@code common.graph} types ({@link Graph},
 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :

 *
 * <h3>Usage</h3>
 *
 * Given an algorithm, for example:
 *
 * {@snippet :
 * public <N> someGraphAlgorithm(N startNode, PredecessorsFunction<N> predecessorsFunction);
 * }
 *
 * you will invoke it depending on the graph representation you're using.
 *
 * <p>If you have an instance of one of the primary {@code common.graph} types ({@link Graph},
 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :

   *
   * <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 {@code true} if the graph was modified as a result of this call

 *
 * <p>Examples of use:
 *
 * {@snippet :
 * // Building a mutable graph
 * MutableGraph<String> graph = GraphBuilder.undirected().allowsSelfLoops(true).build();
 * graph.putEdge("bread", "bread");
 * graph.putEdge("chocolate", "peanut butter");
 * graph.putEdge("peanut butter", "jelly");
 *
 * // Building an immutable graph
 * ImmutableGraph<String> immutableGraph =
 *     GraphBuilder.undirected()

  Set<N> nodes();

  //
  // Graph properties
  //

  /**
   * Returns true if the edges in this graph are directed. Directed edges connect a {@link
   * EndpointPair#source() source node} to a {@link EndpointPair#target() target node}, while
   * undirected edges connect a pair of nodes to each other.
   */
  boolean isDirected();

  /**