def METHOD_NAME(device_mesh, rank):
    # tensor to comm
    tensor_to_comm = torch.ones(2, 2).cuda() * rank
    tensor_to_check = torch.ones(2, 2).cuda() * rank
    dim_partition_dict = {}
    # DistSpec:
    #     shard_sequence: R,R
    #     device_mesh_shape: (2, 2)
    sharding_spec = ShardingSpec(device_mesh, tensor_to_comm.shape, dim_partition_dict=dim_partition_dict)
    comm_spec = CommSpec(CollectiveCommPattern.IDENTITY_FWD_ALLREDUCE_BWD, sharding_spec, logical_process_axis=0)
    tensor_to_comm = comm_spec.covert_spec_to_action(tensor_to_comm)
    assert tensor_to_comm.equal(tensor_to_check)