* Add covariant mutable overriding and overriding variance to rejected ideas
* Update the notes on runtime implementation
* Add one more argument for prohibiting variance overrides
Note: there's an open question about whether interface variance should be inferred or be user-declared (defaulting to invariant unless declared otherwise). The current draft uses inferred invariance. See e.g. discussion at https://github.com/python/peps/pull/243#issuecomment-295826456.
Ivan Levkivskyi
Andreas Pelme
Jelle Zijlstra