code: def __init__(self, target):
      self.target = weakref.ref(target)
  
imports: import weakref
  from abc import ABCMeta, abstractmethod
  import torch
  from pyro.ops import packed
  from pyro.util import jit_iter
label_desc: Use image node_id 1 to create a new _LeafBackward object from inherited base classes: Backward with example: obj = _LeafBackward(target)