concurrent.futures.Future.add_done_callback: calling thread description error.

asyncio.run_coroutine_threadsafe will return a concurrent.futures.Future.
And according to its doc concurrent.futures.Future.add_done_callback() :

Added callables are called in the order that they were added and are always ** called in a thread belonging to the process that added them. **

But acually, the callback is called in where Future.set_result() is called according to its source.

Linked PRs

• gh-122678

从 concurrent.futures.Future.add_done_callback() 文档以及通过 asyncio.run_coroutine_threadsafe 达到的行为开始；将措辞与 Future.set_result() 的源代码路径进行比较。在进行更改之前考虑现有的关联 PR，并确保文档准确描述回调运行所在的线程，即视为完成。