How to make an option required?

[FrankDMartinez]

While I might have missed it in the documentation, I saw nothing about how to make an option mandatory. Can Anyone point Me in the direction of such information?

Thanks in advance.

[itzg]

Since this library builds on the built-in flags package, I hadn't yet found a way to make it indicate an error for required arguments that are missing. As a result, I resort to adding explicit conditionals after the flag loading to check for unset arguments.