class_docstr: Joinable train loop.
class_docstr_tok: ["Joinable","train","loop","."]
docstr: Join caller.
  
  For now, don't do anything.
code: def __call__(self):
      """
      Join caller.
  
      For now, don't do anything.
      """
      Join.notify_join_context(self)
  
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 2 for calling the JoinableTrainLoop obj's underlying member method code with example usage: obj.__call__() without return types