TYP: type all arguments with int default values
This enables the last missing check from autotyping: adding type annotations for int default values.

Some of the `axis` might need some more scrutiny whether they allow only ints or also "index" and "columns". Wouldn't mind postponing that when tightening `Axis` to `Literal[0, 1, "index", "columns", "rows"]`.
Thanks @twoertwein 

> Some of the axis might need some more scrutiny whether they allow only ints or also "index" and "columns".

Yeah definitely. Is there an open issue about this in the issue tracker? IMO public API `axis` args should be able to accept  `Literal[0, 1, "index", "columns", "rows"]` but immediately converted to `0/1` > MO public API `axis` args should be able to accept `Literal[0, 1, "index", "columns", "rows"]` but immediately converted to `0/1`

That is also my assumption/expectation :) however, I think that some of the `self.axis` might also be "index/columns". hopefully can figure it out with mypy+doc-string+some runtime testing.