public interface TreeNodePrePostVisitor<T>
void
visitIn(TreeNode<? extends T> node, int depth, int index, int numSiblings)
visitOut(TreeNode<? extends T> node, int depth, int index, int numSiblings)
void visitIn(TreeNode<? extends T> node, int depth, int index, int numSiblings)
void visitOut(TreeNode<? extends T> node, int depth, int index, int numSiblings)