Feature

Our set.update uses IterNext for iterating given args and update the set contents (makes sense).
But this makes incompatibility with cpython.
cpython's implementation is converting given args to tuple and uses get_size and get_item.
As these method does not go through the iternext, there is no exception if the set is mutated during update.

Python Documentation

https://github.com/python/cpython/blob/3.10/Objects/setobject.c#L930-L941

Related test cases

• test_set.py test_merge_and_mutate