This is the 3rd features that differ this app from others. For programming language which supports class and inheritance, view the hierarchy of the class inheritance will help reader understand the code structures. To view the class inheritance structures, do:

Tap the rectangle twice and you can jump the class definition. The first tap will cause the rectangle being highlighted while the second tap will start to jump to symbol.

Also, on the upper right most on the Navigation bar, tap [Save] button will save the call inheritance graph into your album.