code: def test_asynchronous_exception(self):
      flag = Event()
      assert not flag.is_set()
  
      def closure1():
          flag.set()
          raise RuntimeError("Simulating exception in closure1")
  
      torch._lazy.add_step_closure(closure1, run_async=True)
      torch._lazy.mark_step()
  
      flag.wait(timeout=5)
  
      try:
  
          def closure2():  # Should never execute
              flag.clear()
  
          torch._lazy.add_step_closure(closure2, run_async=True)
          torch._lazy.mark_step()
  
          raise AssertionError()  # Should not reach here
      except RuntimeError as e:
          # Should have caught exception from closure1
          pass
  
      assert flag.is_set()
  
file_path: pytorch/test/lazy/test_step_closures.py
imports: from threading import Event
  from time import sleep
  import torch._lazy
  import torch._lazy.ts_backend
  from torch.testing._internal.common_utils import run_tests, TestCase
label_desc: Use image node_id 4 for calling the ClosuresTest obj's underlying member method code with example usage: obj.test_asynchronous_exception() without return types