code: def test_init_process_group(self):
      device_type = _get_device_type(self.world_size)
      mesh_tensor = torch.arange(4).reshape(2, 2)
      self.assertTrue(not is_initialized())
      _set_env_var(world_size=self.world_size, rank=self.rank)
      DeviceMesh(device_type, mesh_tensor)
      self.assertTrue(is_initialized())
      self.destroy_pg()
  
imports: import os
  import torch
  import torch.distributed._functional_collectives
  from torch.distributed._tensor import DTensor
  from torch.distributed._tensor._collective_utils import mesh_all_to_all, mesh_broadcast, mesh_scatter
  from torch.distributed._tensor.placement_types import _Partial, Shard
  from torch.distributed.device_mesh import _mesh_resources, DeviceMesh, init_device_mesh
  from torch.distributed.distributed_c10d import get_global_rank, get_world_size, init_process_group, is_initialized, is_nccl_available, ProcessGroup
  from torch.testing._internal.common_utils import run_tests
  from torch.testing._internal.distributed._tensor.common_dtensor import DTensorTestBase, with_comms
  from torch.testing._internal.distributed.fake_pg import FakeStore
label_desc: Use image node_id 2 for calling the DeviceMeshTest obj's underlying member method code with example usage: obj.test_init_process_group() without return types