code: def traverse(self, predicate=lambda i, d: True,
                   prune=lambda i, d: False, depth=-1, branch_first=True,
                   visit_once=False, ignore_self=1):
          
          return super(Tree, self).traverse(predicate, prune, depth, branch_first, visit_once, ignore_self)
docs: For documentation, see util.Traversable.traverse
          Trees are set to visit_once = False to gain more performance in the traversal