class_docstr: Join hook for train loop.
  
  Adapted from https://pytorch.org/tutorials/advanced/generic_join.html
class_docstr_tok: ["Join","hook","for","train","loop",".","Adapted","from","https",":","\/\/pytorch.org\/tutorials\/advanced\/generic_join.html"]
code: def __init__(self, train_loop: JoinableTrainLoop):
      self.train_loop = train_loop
  
imports: import contextlib
  import functools
  import torch
  import torch.distributed
  from torch.distributed.algorithms.join import Join, Joinable, JoinHook
  import torch.nn
  from parlai.scripts.eval_model import Evaluator
  from parlai.scripts.train_model import TrainLoop
  from parlai.utils.distributed import is_distributed, get_dist_group
label_desc: Use image node_id 1 to create a new TrainLoopJoinHook object from inherited base classes: JoinHook with example: obj = TrainLoopJoinHook(train_loop)