Nitpick (I think this is just a miswording rather than a misunderstanding): it's not optional. You can have unlabelled args, but that's enforced too: the label

Nitpick (I think this is just a miswording rather than a misunderstanding): it's not optional. You can have unlabelled args, but that's enforced too: the label must be included or omitted at the call site according to the function declaration.