code: def test_default_skip_tracker():
      q = Queue()
  
      def f():
          q.put(current_skip_tracker())
  
      t = threading.Thread(target=f)
      t.start()
      t.join()
  
      skip_tracker = q.get()
  
      assert type(skip_tracker) is SkipTracker
      assert type(skip_tracker) is not SkipTrackerThroughPotals
  
file_path: pytorch/test/distributed/pipeline/sync/skip/test_tracker.py
imports: from queue import Queue
  import threading
  import pytest
  import torch
  from torch import nn
  from torch.distributed.pipeline.sync.checkpoint import enable_checkpointing, enable_recomputing
  from torch.distributed.pipeline.sync.microbatch import Batch
  from torch.distributed.pipeline.sync.skip import pop, skippable, stash
  from torch.distributed.pipeline.sync.skip.layout import SkipLayout
  from torch.distributed.pipeline.sync.skip.tracker import SkipTracker, SkipTrackerThroughPotals, current_skip_tracker
  from torch.testing._internal.common_utils import run_tests
label_desc: Use image node_id 1 for calling a global function with example usage: test_default_skip_tracker() without return types