This fixes an issue with os.PathLike[str] being accepted but not present in the typing. It also uses collections.abc wherever possible instead of typing (can't fully change all of them until 3.9+ is supported, due to runtime requirements). It also uses Sequence/Mapping/Iterable for input parameters (you should be generic in input, specific in output) - doing so adds a few copy functions and improves safety a bit, fewer arguments are allowed to be mutated later this way). A few TypeVars were added - they can be replaced with native syntax in Python 3.12+.

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>