code: def call_at(
          self, when: float, callback: Callable[..., None], *args: Any, **kwargs: Any
      ) -> object:
          
          return self.add_timeout(when, callback, *args, **kwargs)
docs: Runs the ``callback`` at the absolute time designated by ``when``.
  
          ``when`` must be a number using the same reference point as
          `IOLoop.time`.
  
          Returns an opaque handle that may be passed to `remove_timeout`
          to cancel.  Note that unlike the `asyncio` method of the same
          name, the returned object does not have a ``cancel()`` method.
  
          See `add_timeout` for comments on thread-safety and subclassing.
  
          .. versionadded:: 4.0