docstr: Test loading checkpoint with one GPU
code: def test_checkpoint_save_1gpu(self):
      """Test loading checkpoint with one GPU"""
      self.test_checkpoint(save_group_size=1)
  
imports: from contextlib import contextmanager
  import io
  from typing import Callable, Optional, Tuple
  import unittest
  import warnings
  import torch
  from torch.testing._internal import common_utils
  from apex.transformer.testing.distributed_test_base import NcclDistributedTestBase
label_desc: Use image node_id 20 for calling the TestDistributedFusedAdam obj's underlying member method code with example usage: obj.test_checkpoint_save_1gpu() without return types