TYP add some missing types to series

[MarcoGorelli]

Noticed this while working on #40973

Those without any types won't be checked by mypy

e.g.:

$ cat t.py
from typing import final

class Foo:
    @final
    def foo(x) -> None:
        pass

class Bar(Foo):
    def foo(x):
        pass
$ mypy t.py
Success: no issues found in 1 source file

Adding in -> None:

$ cat t.py
from typing import final

class Foo:
    @final
    def foo(x) -> None:
        pass

class Bar(Foo):
    def foo(x) -> None:
        pass
$ mypy t.py
t.py:9: error: Cannot override final attribute "foo" (previously declared in base class "Foo")  [misc]
Found 1 error in 1 file (checked 1 source file)

[jbrockmendel]

Thanks @MarcoGorelli