code: def wait() -> None:
      """Wait for a watched file to change, then restart the process.
  
      Intended to be used at the end of scripts like unit test runners,
      to run the tests again after any source file changes (but see also
      the command-line interface in `main`)
      """
      io_loop = ioloop.IOLoop()
      io_loop.add_callback(start)
      io_loop.start()
  
imports: import os
  import sys
  import functools
  import importlib.abc
  import os
  import pkgutil
  import sys
  import traceback
  import types
  import subprocess
  import weakref
  from tornado import ioloop
  from tornado.log import gen_log
  from tornado import process
  from typing import Callable, Dict, Optional, List, Union
label_desc: Use image node_id 2 for calling a global function with example usage: wait() without return types