bpo-35701: Added '__weakref__' to UUID __slots__ list to prevent regression. by dheiberg · Pull Request #11570 · python/cpython
UUID objects don't currently allow for weak referencing with their new slots implementation. This would cause regressions if people using weak referencing on these objects were to upgrade Python version. Also added a basic regression test that fails without the change implemented.
This is my first PR to cpython, so please let me know if there is something I forgot to do!