I prefer the patch by Inada-san!

>> Describing the default behavior and "from None" is enough for new users
> Strange that you think that "from None" is more useful for beginners than these special attributes.

Doesn’t feel strange to me:  `raise Exc from exc` or `from None` shows how to use the mecanism, whereas the special attributes are about the implementation.  A tutorial can show how to use language features like for loops or with statements, but shouldn’t explain how to implement the protocols, that’s too much detail if you’re just starting to learn programming.