class_docstr: Gather tensors from all TPU workers with support for backward propagation.
code: def forward(ctx, x, dim):
      ctx.dim = dim
      tensor_list = xm.all_gather(x.unsqueeze(dim), dim=dim)
      return tensor_list
  
imports: import contextlib
  import logging
  import os
  import pickle
  import socket
  import subprocess
  import warnings
  from itertools import chain
  import torch
  from mmf.common.registry import registry
  from torch import distributed
label_desc: Use image node_id 1 for calling the XLAGatherLayer obj's underlying member method code with example usage: obj.forward(ctx, x, dim) and returns: tensor_list