Thanks for the tips! I've been using this patch in my own code in a early imported `__init__.py`:

```
from graphlib import TopologicalSorter
from types import GenericAlias

if not hasattr(TopologicalSorter, "__class_getitem__"):  # pragma: no cover
    TopologicalSorter.__class_getitem__ = classmethod(GenericAlias)  # type: ignore
```

Certainly a bit hacky, but aside from no-op on >=3.11 and satisfying mypy, it supports runtime type inspection via `get_type_hints` before 3.11 (which otherwise still errors for stringized versions). The stringized versions are probably a bit simpler/safer for most folks though :)