code: def spawn_callback(self, callback, *args, **kwargs):
          
          with stack_context.NullContext():
              self.add_callback(callback, *args, **kwargs)
docs: Calls the given callback on the next IOLoop iteration.
  
          Unlike all other callback-related methods on IOLoop,
          ``spawn_callback`` does not associate the callback with its caller's
          ``stack_context``, so it is suitable for fire-and-forget callbacks
          that should not interfere with the caller.
  
          .. versionadded:: 4.0