code: 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);
              }
          };
      }
docs: Static factory method for creating an {@link IO} that just returns <code>a</code> when performed.
  
  @param a   the result
  @param <A> the result type
  @return the {@link IO}