Iterable<Character> result = Traverser.forGraph(TWO_TREES).depthFirstPreOrder('a');

    assertEqualCharNodes(result, "ab");
  }

  @Test
  public void forGraph_depthFirstPreOrderIterable_twoTrees() {
    assertEqualCharNodes(Traverser.forGraph(TWO_TREES).depthFirstPreOrder(charactersOf("a")), "ab");
    assertEqualCharNodes(
        Traverser.forGraph(TWO_TREES).depthFirstPreOrder(charactersOf("ac")), "abcd");
  }

        }
        return root;
      }
    },
    RANDOM {
      /**
       * Generates a tree with topology selected uniformly at random from the topologies of binary
       * trees of the specified size.
       */
      @Override
      Optional<BinaryNode> createTree(int size, Random rng) {
        int[] keys = new int[size];

    Iterable<Character> result = Traverser.forGraph(TWO_TREES).depthFirstPreOrder('a');

    assertEqualCharNodes(result, "ab");
  }

  @Test
  public void forGraph_depthFirstPreOrderIterable_twoTrees() {
    assertEqualCharNodes(Traverser.forGraph(TWO_TREES).depthFirstPreOrder(charactersOf("a")), "ab");
    assertEqualCharNodes(
        Traverser.forGraph(TWO_TREES).depthFirstPreOrder(charactersOf("ac")), "abcd");
  }

org.checkerframework.framework.util.typeinference.constraint
org.checkerframework.framework.util.typeinference.solver
org.checkerframework.javacutil
org.checkerframework.javacutil.dist
org.checkerframework.javacutil.trees
org.eclipse.jdt.annotation
org.eclipse.jgit.annotations
org.jetbrains.annotations
org.jmlspecs.annotation
org.netbeans.api.annotations.common

org.checkerframework.framework.util.typeinference.constraint
org.checkerframework.framework.util.typeinference.solver
org.checkerframework.javacutil
org.checkerframework.javacutil.dist
org.checkerframework.javacutil.trees
org.eclipse.jdt.annotation
org.eclipse.jgit.annotations
org.jetbrains.annotations
org.jmlspecs.annotation
org.netbeans.api.annotations.common

  public static <N> Traverser<N> forTree(SuccessorsFunction<N> tree) {
    if (tree instanceof BaseGraph) {
      checkArgument(((BaseGraph<?>) tree).isDirected(), "Undirected graphs can never be trees.");
    }
    if (tree instanceof Network) {
      checkArgument(((Network<?, ?>) tree).isDirected(), "Undirected networks can never be trees.");
    }
    return new Traverser<N>(tree) {
      @Override
      Traversal<N> newTraversal() {

        }
        return root;
      }
    },
    RANDOM {
      /**
       * Generates a tree with topology selected uniformly at random from the topologies of binary
       * trees of the specified size.
       */
      @Override
      Optional<BinaryNode> createTree(int size, Random rng) {
        int[] keys = new int[size];

import java.util.Deque;
import java.util.Iterator;
import java.util.Queue;
import javax.annotation.CheckForNull;

/**
 * Views elements of a type {@code T} as nodes in a tree, and provides methods to traverse the trees
 * induced by this traverser.
 *
 * <p>For example, the tree
 *
 * <pre>{@code
 *        h
 *      / | \
 *     /  e  \
 *    d       g
 *   /|\      |
 *  / | \     f
 * a  b  c
 * }</pre>
 *

  It sounded an excellent plan, no doubt, and very neatly and
simply arranged; the only difficulty was, that she had not the
smallest idea how to set about it; and while she was peering
about anxiously among the trees, a little sharp bark just over
her head made her look up in a great hurry.

  An enormous puppy was looking down at her with large round
eyes, and feebly stretching out one paw, trying to touch her.

 *
 * <p>For {@code ImmutableMultiset} in particular, I ran into a problem with the {@code
 * GwtSerializationDependencies} approach: When autogenerating a serializer for the new class, GWT
 * tries to refer to our dummy serializer for the superclass,
 * ImmutableMultiset_CustomFieldSerializer. But that type has no methods (since it's never actually