* {@code com.google.common.graph.Traverser}.
 */
@SuppressWarnings("DefaultPackage")
public class TraverserRewrite {
  abstract class TreeTraverserPreOrder<N> {
    @Placeholder
    abstract Iterable<N> getChildren(N node);

    @BeforeTemplate
    Iterable<N> before1(N root) {
      return TreeTraverser.using((N node) -> getChildren(node)).preOrderTraversal(root);