docs: @Override
      public final <C, D> These<C, D> biMap(Function<? super A, ? extends C> lFn,
                                            Function<? super B, ? extends D> rFn) {
          return match(a -> a(lFn.apply(a)), b -> b(rFn.apply(b)), into((a, b) -> both(lFn.apply(a), rFn.apply(b))));
      }