code: def current(instance=True):
          
          current = getattr(IOLoop._current, "instance", None)
          if current is None and instance:
              current = None
              #if asyncio is not None:
              #    from tornado.platform.asyncio import AsyncIOLoop, AsyncIOMainLoop
              #    if IOLoop.configured_class() is AsyncIOLoop:
              #        current = AsyncIOMainLoop()
              if current is None:
                  if sys.platform == 'darwin':
                      from .platforms import KQueueIOLoop
                      current = KQueueIOLoop()
                  else:
                      from .platforms import EPollIOLoop
                      current = EPollIOLoop()
                  current.initialize()
                  #current = IOLoop()
              if IOLoop._current.instance is not current:
                  raise RuntimeError("new IOLoop did not become current")
          return current
docs: Returns the current thread's `IOLoop`.
  
          If an `IOLoop` is currently running or has been marked as
          current by `make_current`, returns that instance.  If there is
          no current `IOLoop` and ``instance`` is true, creates one.
  
          .. versionchanged:: 4.1
             Added ``instance`` argument to control the fallback to
             `IOLoop.instance()`.
          .. versionchanged:: 5.0
             The ``instance`` argument now controls whether an `IOLoop`
             is created automatically when there is none, instead of
             whether we fall back to `IOLoop.instance()` (which is now
             an alias for this method)