new_contents: import asyncio
  import sys
  
  # Use the selector event loop on windows. Do this in tornado/test/__init__.py
  # instead of runtests.py so it happens no matter how the test is run (such as
  # through editor integrations).
  if sys.platform == "win32" and hasattr(asyncio, "WindowsSelectorEventLoopPolicy"):
      asyncio.set_event_loop_policy(asyncio.WindowsSelectorEventLoopPolicy())  # type: ignore
  
subject: Use selector event loop on windows.