code: def _fix_tornado_crash() -> None:
      """Set default asyncio policy to be compatible with Tornado 6.
  
      Tornado 6 (at least) is not compatible with the default
      asyncio implementation on Windows. So here we
      pick the older SelectorEventLoopPolicy when the OS is Windows
      if the known-incompatible default policy is in use.
  
      This has to happen as early as possible to make it a low priority and
      overridable
  
      See: https://github.com/tornadoweb/tornado/issues/2608
  
      FIXME: if/when tornado supports the defaults in asyncio,
      remove and bump tornado requirement for py38
      """
      if env_util.IS_WINDOWS:
          try:
              from asyncio import (  # type: ignore[attr-defined]
                  WindowsProactorEventLoopPolicy,
                  WindowsSelectorEventLoopPolicy,
              )
          except ImportError:
              pass
              # Not affected
          else:
              if (
                  type(asyncio.get_event_loop_policy())
                  is WindowsProactorEventLoopPolicy
              ):
                  # WindowsProactorEventLoopPolicy is not compatible with
                  # Tornado 6 fallback to the pre-3.8 default of Selector
                  asyncio.set_event_loop_policy(
                      WindowsSelectorEventLoopPolicy()
                  )
  
imports: import asyncio
  import os
  import signal
  import sys
  from pathlib import Path
  from typing import Any, Dict, List
  import click
  from streamlit import config, env_util, file_util, net_util, secrets, url_util, util, version
  from streamlit.config import CONFIG_FILENAMES
  from streamlit.git_util import MIN_GIT_VERSION, GitRepo
  from streamlit.logger import get_logger
  from streamlit.source_util import invalidate_pages_cache
  from streamlit.watcher import report_watchdog_availability, watch_dir, watch_file
  from streamlit.web.server import Server, server_address_is_unix_socket, server_util
label_desc: Use image node_id 4 for calling a global function with example usage: _fix_tornado_crash() without return types