class_docstr: Marks the boundary between two joined (nested) pytrees.
class_docstr_tok: ["Marks","the","boundary","between","two","joined","(","nested",")","pytrees","."]
code: def __init__(self, subtree):
      self.subtree = subtree
  
imports: from __future__ import annotations
  from typing import Any, Callable, NamedTuple
  from collections import namedtuple
  import functools
  from functools import partial
  import jax.numpy
  from jax._src.util import safe_zip, safe_map, unzip2
  from jax import tree_util
  from jax.tree_util import tree_map, tree_flatten, tree_unflatten, register_pytree_node
label_desc: Use image node_id 1 to create a new JoinPoint object  with example: obj = JoinPoint(subtree)