> this limitation to the latin-1 subset is not compatible with the documentation, which says that valid Python identifiers are valid group names.

Not all latin-1 characters are valid identifier, for example:

    >>> '\x94'.encode('latin1')
    b'\x94'
    >>> '\x94'.isidentifier()
    False

There is a workaround, you can convert `bytes` to `str` with "latin-1" decoder before processing, IIRC there will be no extra overhead (memory/speed) during processing, then the name and content are the same type. :)