I worried about people think we recommend it when we support it, while this is just a request from one person, not recommendation after wide discussion.

But it doesn't affect to static tools than I suspected. Tools like autocompletion should support  cached_property in normal class anyway.

And this pull request doesn't promote the cached_property support in the document.
So I don't have a strong objections for now.


Generally speaking, I don't like this type of changes.
Some people think it's improvement, but since there are no clear vision/recommendation how ABCs are used, it's just a random increasing code.
We can't maintain "preferably only one obvious way" for now, especially about ABCs.