btw, I never did this in my library because I didn't need to, but you could also support an operation that computes SCC's to minimize the groups without freezin

btw, I never did this in my library because I didn't need to, but you could also support an operation that computes SCC's to minimize the groups without freezing the graph. The minimized groups would still merge with other groups if you created links between them. But this would be a way to make the refcounting more precise without strictly requiring that subgraphs become immutable.