@garybernhardt reports (in a tweet!): "garybernhardt @nedbat A file with just "class Foo:\n pass" has Branch=2. Feels like a bug; is it one?"
In the compiled code, line 1 can go next to two different places: line 2 or leave the file. That's why there are two branch possibilities in the code. But there's conceptually no branch here, so we should figure out a way to considering it as a branch.