On Thu, May 13, 2021 at 10:28 AM Antoine Pitrou <antoine@python.org> wrote:

 I agree that <optional> is a reasonable spelling.

I initially suggested <optional>, but now I'm not sure because it doesn't indicate what happens when you don't provide it (as in, what is the default value).  So now I'm with <derived> or <implicit>.

The arg is only there for backwards compatibility now.