async def METHOD_NAME(app: App):
    """
    An application ``on_startup`` callback that initializes a
    :class:`~ThreadPoolExecutor` and attaches it to the ``app`` object.
    :param app: the application object
    """
    loop = asyncio.get_event_loop()
    process_executor = ProcessPoolExecutor()
    async def run_in_process(func, *args):
        return await loop.run_in_executor(process_executor, func, *args)
    app["run_in_process"] = run_in_process
    app["process_executor"] = process_executor