The OpenG Dictionary Library package contains a library for key-value sets.
Install the OpenG Dictionary Library with VIPM (a.k.a oglib_dictionary)
Take a look at the Help Wanted issues list. If it's your first contribution or you're not extremely familiar with this library, you might want to look at the Good First Issues list. If you see an issue that looks like one you can complete, add a comment to the issue stating you'd like to work on it, and a maintainer will follow up and "assigned" to you. You then create a branch and then submit your contribution in the form of a Pull Requests.