docs: public static <A> IO<A> io(A a) {
          return new IO<A>() {
              @Override
              public A unsafePerformIO() {
                  return a;
              }
  
              @Override
              public CompletableFuture<A> unsafePerformAsyncIO(Executor executor) {
                  return completedFuture(a);
              }
          };
      }