* that is how the signature looked even prior to this comment! So naturally any change can break
 * existing users, but it can't *fix* existing users because any users who needed
 * `Function<@Nullable A, @Nullable B>` already had to find a workaround. Still, there is a *ton* of
 * fallout from trying to switch. I would be shocked if the switch would offer benefits to anywhere
 * near enough users to justify the costs.
 *