I don't have anything to add on the side of the technical specifics, but I
do want to point out another benefit of adding these APIs: a significant
improvement in testability, since you will be able to test the reduction
and reconstruction behaviours directly, rather than having to infer what is
go
Some additional things that might be worth doing. I believe this exposes enough
to allow people to build an object graph walker out of the `pickle`/`copy`
protocol without having to access fragile internals, and without restricting
future evolution of the internals of the protocol. See [the same
