fix: checks type for nested subparsers

[jduf]

this fails:

def get_parser_2() -> ArgumentParser:
    parser = ArgumentParser(prog="prog")

    sub_parser = parser.add_subparsers(dest="command")
    command = sub_parser.add_parser("parent")
    command.add_argument("key")

    sub_sub_parser = command.add_subparsers(dest="subcommand")
    subcommand = sub_sub_parser.add_parser("child")
    subcommand.add_argument("--b", action="store_true")

    return parser

[gaborbernat]

Needs test.

[jduf]

I would be happy to try to fix my PR but I don't know how to run the tests on my machine...

[gaborbernat]

I would be happy to try to fix my PR but I don't know how to run the tests on my machine...

We're using tox, read https://tox.wiki/en/4.58.0/.

[jduf]

Okay, I added one test function and a related test directory in root. I hope what I did respects your requirements. It's the first time I create a PR and work with tox... I hope my PR is helpful!