Python version

[hwq0726]

Hi,

It seems the requirement for Python version should be 3.10 or higher (in order to use "type union" the | operator). I was trying to use Python 3.9 and met TypeError: unsupported operand type(s) for |: 'ABCMeta' and 'NoneType' when from synthid_text import detector_mean.
However, the requires-python specification in pyproject.toml lists >=3.9, which may lead to compatibility issues for users on Python 3.9.

Thank you for your attention.

[RyanMullins]

Thanks for the big report. Thought we had reverted all those for 3.9 compatibility but must've missed some. I'll give it a look next week, but also happy to review a PR if you want to send one.