What is the best way to access a sub group for type hints?

[haarisr]

 def write(root: zarr.Group, data:np.ndarray):
        group = root["foo/bar"]
        group.array("baz", data)

I have already create root["foo/bar"]. When I want to access it, the type hint says that group is either an Array or Group. How can I just extract a group?

[d-v-b]

the type checker cannot know that root["foo/bar"] will be a zarr group. Consider the possibility that some other program on your computer deleted the group at foo/bar, or replaced it with an array. But if you are sure that it's a group, you can use typing.cast to assert this to the type checker.

In the future, we could add a get_group(group_name) method that either returns a group or errors. this would be type-safe.