In native code, typed Maps (Z883) are deserialized to hash maps. There is no restriction in Wikifunctions on what types can serve as Map keys. This means that all deserialized ZObjects must be hashable.

In Python, this means that

1. Typed Lists (Z881) should deserialize to Python tuples (instead of lists, as at present).
2. Typed Maps (Z883) should deserialize to a custom extension of dict which is immutable and implements __hash__ and __eq__.
3. The ZObject and ZPair classes (from function-evaluator::executors/python3/utils.py) must implement __hash__ (they already implement __eq__).

In JavaScript, we probably need to do something similar, but I don't know JS well enough to say extemporaneously what makes a good Map key 😿