1. You are right, it doesn't do what I expect. I think I actually need something like `'/'.split('path/to/file')` because this is a URL parser (not an OS path). This is where I need to (as you said) explicitly say in the docstrings that this only accepts a URL path as an argument.

2. I don't think `url_path_join` works in this case, because I strip the `/` away to encode each part. That method needs the forward slash to be included. I probably need just need to do `'/'.join(...)`.