In `_typing.pyi`, we have: ```python Axis = Union[str, int] SeriesAxisType = Literal["index", 0] # Restricted subset of _AxisType for series AxisType = Literal["columns", "index", 0, 1] ``` There are 23 places (assuming I did `grep` correctly) where we use `Axis`, but can probably change this to `AxisType` in many (if not all) of them.