code: def checkpoint_mode_invalid(pipe_class):
      model = nn.Sequential(nn.Linear(1, 1))
  
      with pytest.raises(
          ValueError,
          match="checkpoint is not one of 'always', 'except_last', or 'never'",
      ):
          pipe_class(
              model,
              balance=[1],
              worker_map=get_worker_map(),
              chunks=2,
              checkpoint="INVALID_CHECKPOINT",
          )
  
imports: from collections import OrderedDict
  from copy import deepcopy
  import os
  import time
  import pytest
  import torch
  from torch import nn
  from fairscale.fair_dev.testing.testing import get_worker_map, torch_spawn
  from fairscale.internal import torch_version
  from fairscale.nn.model_parallel.initialize import get_pipeline_parallel_group
  from fairscale.nn.pipe import AsyncPipe
  from fairscale.nn.pipe.types import LazyModule
label_desc: Use image node_id 15 for calling a global function with example usage: checkpoint_mode_invalid(pipe_class) without return types