code: def test_allgather(self):
      input_tensor = torch.ones(3, 3) * dist.get_rank()
      output_tensors = [
          torch.empty_like(input_tensor) for _ in range(self.world_size)
      ]
      dist.all_gather(output_tensors, input_tensor)
      for rank, out_tensor in enumerate(output_tensors):
          self.assertEqual(out_tensor, torch.ones(3, 3) * rank)
  
imports: import os
  import sys
  import torch
  import torch.distributed
  from torch._C._distributed_c10d import ReduceOp
  from unittest import skip, SkipTest
  import operator
  from functools import reduce
  import threading
  import torch.autograd
  from torch.testing._internal.common_distributed import spawn_threads_and_init_comms, MultiThreadedTestCase, skip_if_lt_x_gpu
  from torch.testing._internal.common_utils import TestCase, run_tests, IS_SANDCASTLE
label_desc: Use image node_id 4 for calling the TestCollectivesWithBaseClass obj's underlying member method code with example usage: obj.test_allgather() without return types