checkNotNull(nodeToChildrenFunction);
    return new TreeTraverser<T>() {
      @Override
      public Iterable<T> children(T root) {
        return nodeToChildrenFunction.apply(root);
      }
    };
  }

  /** Returns the children of the specified node. Must not contain null. */
  public abstract Iterable<T> children(T root);

  /**

    final List<Tree> children;

    public Tree(char value, Tree... children) {
      super(value);
      this.children = Arrays.asList(children);
    }
  }

  private static final TreeTraverser<Tree> ADAPTER =
      new TreeTraverser<Tree>() {
        @Override
        public Iterable<Tree> children(Tree node) {
          return node.children;
        }
      };

    final List<Tree> children;

    public Tree(char value, Tree... children) {
      super(value);
      this.children = Arrays.asList(children);
    }
  }

  private static final TreeTraverser<Tree> ADAPTER =
      new TreeTraverser<Tree>() {
        @Override
        public Iterable<Tree> children(Tree node) {
          return node.children;
        }
      };

  }

  private static final TreeTraverser<BinaryNode> VIEWER =
      new TreeTraverser<BinaryNode>() {
        @Override
        public Iterable<BinaryNode> children(BinaryNode root) {
          return Optional.presentInstances(ImmutableList.of(root.left, root.right));
        }
      };

  enum Traversal {
    PRE_ORDER {
      @Override

                   JDK6-like APIs.

                   So instead, we use javac9, which doesn't lead to this error.
              -->
              <compilerArgs combine.children="append">
                <arg>-J-Xbootclasspath/p:${settings.localRepository}/com/google/errorprone/javac/${javac.version}/javac-${javac.version}.jar</arg>
              </compilerArgs>
            </configuration>

  <build>
    <resources>
      <resource>
        <directory>..</directory>
        <includes>
          <include>LICENSE</include> <!-- copied from the parent pom because I couldn't figure out a way to make combine.children="append" work -->
          <include>proguard/*</include>
        </includes>
        <targetPath>META-INF</targetPath>
      </resource>
    </resources>
    <plugins>
      <plugin>

    idx++;

    if (c != '?' && c != ',') {
      while (idx < encodedLen) {
        // Read all the children
        idx += doParseTrieToBuilder(stack, encoded, idx, builder);

        if (encoded.charAt(idx) == '?' || encoded.charAt(idx) == ',') {
          // An extra '?' or ',' after a child node indicates the end of all children of this node.
          idx++;
          break;
        }
      }
    }

Alice was not going to do THAT in a hurry.  `No, I'll look
first,' she said, `and see whether it's marked "poison" or not';
for she had read several nice little histories about children who
had got burnt, and eaten up by wild beasts and other unpleasant
things, all because they WOULD not remember the simple rules
their friends had taught them:  such as, that a red-hot poker

  }

  private static final TreeTraverser<BinaryNode> VIEWER =
      new TreeTraverser<BinaryNode>() {
        @Override
        public Iterable<BinaryNode> children(BinaryNode root) {
          return Optional.presentInstances(ImmutableList.of(root.left, root.right));
        }
      };

  enum Traversal {
    PRE_ORDER {
      @Override

  <build>
    <resources>
      <resource>
        <directory>..</directory>
        <includes>
          <include>LICENSE</include> <!-- copied from the parent pom because I couldn't figure out a way to make combine.children="append" work -->
          <include>proguard/*</include>
        </includes>
        <targetPath>META-INF</targetPath>
      </resource>
    </resources>
    <plugins>
      <plugin>