"register_random()" has used "weakref" since 6.27.1 - 2021-11-22,
allowing the "Random"-compatible objects to be garbage-collected when
there are no other references remaining in order to avoid memory
leaks. We now raise an error or emit a warning when this seems likely
to happen immediately.
The type annotation of "register_random()" was also widened so that
structural subtypes of "Random" are accepted by static typecheckers.
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