put asyncio fix into a function to make it more obvious where it starts and ends

import signal

import re

import warnings

import asyncio

from fastapi import FastAPI

from fastapi.middleware.cors import CORSMiddleware

from fastapi.middleware.gzip import GZipMiddleware

else:

    server_name = "0.0.0.0" if cmd_opts.listen else None

def fix_asyncio_event_loop_policy():

    """

        The default `asyncio` event loop policy only automatically creates

        event loops in the main threads. Other threads must create event

        loops explicitly or `asyncio.get_event_loop` (and therefore

        `.IOLoop.current`) will fail. Installing this policy allows event

        loops to be created automatically on any thread, matching the

        behavior of Tornado versions prior to 5.0 (or 5.0 on Python 2).

    """

    import asyncio

    if sys.platform == "win32" and hasattr(asyncio, "WindowsSelectorEventLoopPolicy"):

        # "Any thread" and "selector" should be orthogonal, but there's not a clean

        # interface for composing policies so pick the right base.

    else:

        _BasePolicy = asyncio.DefaultEventLoopPolicy

    class AnyThreadEventLoopPolicy(_BasePolicy):  # type: ignore

        """Event loop policy that allows loop creation on any thread.

    The default `asyncio` event loop policy only automatically creates

    event loops in the main threads. Other threads must create event

    loops explicitly or `asyncio.get_event_loop` (and therefore

    `.IOLoop.current`) will fail. Installing this policy allows event

    loops to be created automatically on any thread, matching the

    behavior of Tornado versions prior to 5.0 (or 5.0 on Python 2).

        Usage::

            asyncio.set_event_loop_policy(AnyThreadEventLoopPolicy())

    .. versionadded:: 5.0

        """

        def get_event_loop(self) -> asyncio.AbstractEventLoop:

                self.set_event_loop(loop)

                return loop

    asyncio.set_event_loop_policy(AnyThreadEventLoopPolicy())

def initialize():

    fix_asyncio_event_loop_policy()

    check_versions()

    extensions.list_extensions()