A snapshot of an object's internal state, as an opaque map: Monty's memento.py.

Monty defines Memento as Mapping[str, Any] and nothing more — the shape is deliberately not specified, because a memento is only ever handed back to the object that made it. What a caller may do with one is save it, log it, or give it back; reading a key out of it is what every logging bug looks like.

Here the same holds, with the one addition Python does not need: an Elixir map can be pattern-matched by anyone, so the discipline is written down instead of being enforced by the type.