If you want this to work you have to pass the namespace where B is defined as locals to get_type_hint(). The recommended approach is to make B a global class; where that is not possible (as in your second example) you should chose a different name.

We're not going to guess additional namespaces to add to the lookup, so I will close this as won't fix.

PS. For short code snippets like your examples, I prefer pasting the code inline.