class_docstr: This class tests all member functions of crypten package
code: def test_all_gather(self) -> None:
      tensor = torch.tensor([self.rank])
      result = comm.get().all_gather(tensor)
      self.assertEqual(
          result,
          [torch.tensor([rank]) for rank in range(self.world_size)],
      )
  
imports: import unittest
  import crypten
  import crypten.communicator
  import numpy
  import torch
  import torch.distributed
  import torch.nn
  import torch.nn.functional
  from crypten.common import serial
  from crypten.config import cfg
  from test.multiprocess_test_case import get_random_test_tensor, MultiProcessTestCase
label_desc: Use image node_id 7 for calling the TestCommunicator obj's underlying member method code with example usage: obj.test_all_gather() without return types