return newBuilder;
  }

  /**
   * Specifies the order of iteration for the elements of {@link ValueGraph#edges()}, {@link
   * ValueGraph#adjacentNodes(Object)}, {@link ValueGraph#predecessors(Object)}, {@link
   * ValueGraph#successors(Object)} and {@link ValueGraph#incidentEdges(Object)}.
   *
   * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For

    return newBuilder;
  }

  /**
   * Specifies the order of iteration for the elements of {@link ValueGraph#edges()}, {@link
   * ValueGraph#adjacentNodes(Object)}, {@link ValueGraph#predecessors(Object)}, {@link
   * ValueGraph#successors(Object)} and {@link ValueGraph#incidentEdges(Object)}.
   *
   * <p>The default value is {@link ElementOrder#unordered() unordered} for mutable graphs. For

import com.google.errorprone.annotations.Immutable;
import com.google.errorprone.annotations.InlineMe;

/**
 * A {@link ValueGraph} whose elements and structural relationships will never change. Instances of
 * this class may be obtained with {@link #copyOf(ValueGraph)}.
 *
 * <p>See the Guava User's Guide's <a
 * href="https://github.com/google/guava/wiki/GraphsExplained#immutable-implementations">discussion

  private static final class TransposedValueGraph<N, V> extends ForwardingValueGraph<N, V> {
    private final ValueGraph<N, V> graph;

    TransposedValueGraph(ValueGraph<N, V> graph) {
      this.graph = graph;
    }

    @Override
    ValueGraph<N, V> delegate() {
      return graph;
    }

    @Override
    public Set<N> predecessors(N node) {

  private static final class TransposedValueGraph<N, V> extends ForwardingValueGraph<N, V> {
    private final ValueGraph<N, V> graph;

    TransposedValueGraph(ValueGraph<N, V> graph) {
      this.graph = graph;
    }

    @Override
    ValueGraph<N, V> delegate() {
      return graph;
    }

    @Override
    public Set<N> predecessors(N node) {

 * }
 *
 * 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 :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code SuccessorsFunction}. It will also work with

 * }
 *
 * 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 :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code PredecessorsFunction}. It will also work

 * }
 *
 * 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 :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code SuccessorsFunction}. It will also work with

    MutableValueGraph<String, Integer> valueGraph = ValueGraphBuilder.directed().build();
    valueGraph.putEdgeValue("a", "b", 11);

    Traverser.forTree(valueGraph); // Does not throw
  }

  @Test
  public void forTree_withUndirectedValueGraph_throws() throws Exception {
    MutableValueGraph<String, Integer> valueGraph = ValueGraphBuilder.undirected().build();
    valueGraph.putEdgeValue("a", "b", 11);

    MutableValueGraph<String, Integer> valueGraph = ValueGraphBuilder.directed().build();
    valueGraph.putEdgeValue("a", "b", 11);

    Traverser.forTree(valueGraph); // Does not throw
  }

  @Test
  public void forTree_withUndirectedValueGraph_throws() throws Exception {
    MutableValueGraph<String, Integer> valueGraph = ValueGraphBuilder.undirected().build();
    valueGraph.putEdgeValue("a", "b", 11);