hello
I am sorry to bother you. I saw your code, and there is a question i cannot understand. As shown in the figure,is it because you set the levels value to 2? In the bottom_up block, you gave other levels except the last one. And in the top_down block, you just give the last level. why?
![image](https://user-images.githubusercontent.com/88227513/163163412-fe1290bb-39c5-4823-94f1-5c037336e36b.png)