Example suggestion: Ensuring that an argument is a list of strings. I can't be the only one who wasted hours of debugging because I accidentally fed a string to a function expecting a list of strings.

Thank you for suggestion, I have added a simple example.

Can I use the generics introduced with the new type annotations in Python 3.5, so I can refer to Sequence[str] or something like that?

The problem is that every string is, internally, also a sequence of (single-character) strings. So it's not that easy.