class_docstr: This class tests all member functions of crypten package
code: def test_gather(self) -> None:
      tensor = torch.tensor([self.rank])
      for rank in range(self.world_size):
          result = comm.get().gather(tensor, rank)
          if rank == self.rank:
              self.assertEqual(
                  result, [torch.tensor([0]), torch.tensor([1])]
              )
          else:
              self.assertIsNone(result[0])
  
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 5 for calling the TestCommunicator obj's underlying member method code with example usage: obj.test_gather() without return types