task.add_done_callback does not work on task.current_task

[dlashua]

@time_trigger('startup')
def startup():
    log.info('starting')
    my_task = task.current_task()
    task.add_done_callback(my_task, all_done)
    task.sleep(5)

def all_done():
    log.info('task has ended')

The above code results in the following error:

2021-01-13 06:19:48 ERROR (MainThread) [custom_components.pyscript.scripts.test.uniq2.startup] Exception in <scripts.test.uniq2.startup> line 7:
        task.add_done_callback(my_task, all_done)
                                        ^
KeyError: <Task pending name='Task-6896361' coro=<Function.run_coro() running at /config/custom_components/pyscript/function.py:419>>
Traceback (most recent call last):
  File "/config/custom_components/pyscript/eval.py", line 827, in aeval
    val = await getattr(self, name, self.ast_not_implemented)(arg)
  File "/config/custom_components/pyscript/eval.py", line 1757, in ast_call
    return await self.call_func(func, func_name, *args, **kwargs)
  File "/config/custom_components/pyscript/eval.py", line 1787, in call_func
    return await func(*args, **kwargs)
  File "/config/custom_components/pyscript/trigger.py", line 178, in user_task_add_done_callback
    Function.task_add_done_callback(task, ast_ctx, callback, *args, **kwargs)
  File "/config/custom_components/pyscript/function.py", line 472, in task_add_done_callback
    cls.task2cb[task]["cb"][callback] = [ast_ctx, args, kwargs]
KeyError: <Task pending name='Task-6896361' coro=<Function.run_coro() running at /config/custom_components/pyscript/function.py:419>>