to accomplish this functionality, it's better to let addArchiveType support adding archive_type with compression_type.
And the values of compression_type are limited to 'tar', 'zip' by implementation so far, so we could check the values in addArchiveType too. On the other hand, we can just ignore invalid/not-implemented values. What do you think?

sure, it make sense to check compression_type in addArchiveType. All fixed in PR now.

I think None is better than '' here, so the default value of compression_type can be None.

And this part could be

    convert_value(compression_type, cast=str, none_allowed=True, check_only=True)
    if compression_type not in ['zip', 'tar', None]:
        ...

ok, when we want to use None, yes, we can do it like you wrote...so, updated with None value.

:thumbsup:

Commit 576d04ed fixes this pull-request