Another option for code using Python <3.11, that will work without the `from __future__ import annotations` import, is to do something like this:

```
from graphlib import TopologicalSorter
x: 'TopologicalSorter[str]' = TopologicalSorter({"a": {}, "b": {"a"}})
```

By using a string as the annotation, we give mypy the specificity it needs, but the expression will never need to be resolved at runtime.