super(inputFuture, function);
    }

    @Override
    ListenableFuture<? extends O> doTransform(
        AsyncFunction<? super I, ? extends O> function, @ParametricNullness I input)
        throws Exception {
      ListenableFuture<? extends O> outputFuture = function.apply(input);
      checkNotNull(
          outputFuture,