code: def test_stash_none():
      @skippable(stash=["foo"])
      class Stash(nn.Module):
          def forward(self, input):
              yield stash("foo", None)
              return input * 2  # noqa: B901
  
      l1 = Stash()
      l1(torch.tensor(42))
  
file_path: pytorch/test/distributed/pipeline/sync/skip/test_stash_pop.py
imports: import pytest
  import torch
  from torch import nn
  from torch.distributed.pipeline.sync.skip import pop, skippable, stash
  from torch.distributed.pipeline.sync.skip.tracker import SkipTracker, use_skip_tracker
  from torch.testing._internal.common_utils import run_tests
label_desc: Use image node_id 8 for calling a global function with example usage: test_stash_none() and returns: unknown