Backward compatibility for Python < 3.9.

[bomtorazek]

Hi, thank you for your work.

3938023#diff-e654cfbf24c60f251cb36c0b9ca963a78d44853ff3e0c4c137e6b5499227a0aaR71
(os.PathLike[str])

This line requires the Python version to be higher than or equal to 3.9.
In addition, something like these (list[str], tuple[dict[str, Any], str]) also causes a problem.
It would be better if we can use PyGlove with the Python < 3.9 without any errors.