code: def test_sneaky_frame_object_teardown(self):
      class SneakyDel:
          def __del__(self):
              """
              Stash a reference to the entire stack for walking later.
  
              It may look crazy, but you'd be surprised how common this is
              when using a test runner (like pytest). The typical recipe is:
              ResourceWarning + -Werror + a custom sys.unraisablehook.
              """
              nonlocal sneaky_frame_object
              sneaky_frame_object = sys._getframe()
  
      class SneakyThread(threading.Thread):
          """
          A separate thread isn't needed to make this code crash, but it does
          make crashes more consistent, since it means sneaky_frame_object is
          backed by freed memory after the thread completes!
          """
  
          def run(self):
              """Run SneakyDel.__del__ as this frame is popped."""
              ref = SneakyDel()
  
      sneaky_frame_object = None
      t = SneakyThread()
      t.start()
      t.join()
      # sneaky_frame_object can be anything, really, but it's crucial that
      # SneakyThread.run's frame isn't anywhere on the stack while it's being
      # torn down:
      self.assertIsNotNone(sneaky_frame_object)
      while sneaky_frame_object is not None:
          self.assertIsNot(
              sneaky_frame_object.f_code, SneakyThread.run.__code__
          )
          sneaky_frame_object = sneaky_frame_object.f_back
  
imports: import gc
  import operator
  import re
  import sys
  import textwrap
  import threading
  import types
  import unittest
  import weakref
  from test import support
  from test.support import threading_helper
  from test.support.script_helper import assert_python_ok
label_desc: Use image node_id 3 for calling the TestIncompleteFrameAreInvisible obj's underlying member method code with example usage: obj.test_sneaky_frame_object_teardown() without return types