Irwin lastl

Actually, none of this multi-line comment needs to stay here after you implement the actual code.. I just stuck it in as a place holder for you to refer to as you implement it, but the original version of this is in old-scripts/kga/ anyway. If you feel inspired, you can replace it with a docstring for the method itself, but I'd only really spend time on that if there's anything non-obvious from reading the method signature & argparse parser stuff.