addressed all raised questions below: conducting new experiments to compare with hand-designed optimizers (# 1)

We genuinely appreciate all three reviewers' (#1,#2,#3,#4) valuable suggestions to strengthen our paper. More details are referred to Reviewer #3's Q2. We sincerely appreciate your suggestion and will revise the caption in figure 4 for better readability. Reply: It is a great observation. Thus, IL appears to be a main contributor for L2O generalizing across different optimizees.