code: def test_pop():
      @skippable(stash=["foo"])
      class Stash(nn.Module):
          def forward(self, input):
              yield stash("foo", input)
              return input * 2
  
      @skippable(pop=["foo"])
      class Pop(nn.Module):
          def forward(self, input):
              foo = yield pop("foo")
              return foo
  
      l1 = Stash()
      l2 = Pop()
  
      output = l2(l1(torch.tensor(42)))
  
      assert output.item() == 42
  
file_path: fairscale/tests/nn/pipe/skip/test_stash_pop.py
imports: import pytest
  import torch
  from torch import nn
  from fairscale.nn.pipe.skip import pop, skippable, stash
  from fairscale.nn.pipe.skip.tracker import SkipTracker, use_skip_tracker
label_desc: Use image node_id 3 for calling a global function with example usage: test_pop() and returns: unknown, foo