cstl | STL style library in C | 3D Printing library

I have a few classes that use one another: Lanes is a property of Directions, Directions is a property of Diagram. This is a method in Diagram class, it supposes to 'push' information from a list (phsr_lst) to Diagram -> Directions -> Lanes. When I print the data I pushed using getattr(key_lan, cur_arrow) right after setattr(), I get the right data, but when printing it outside the method, it shows as if nothing was changed. When I checked the memory address inside and outside the method, I got different addresses;

This is not the only method that I have that does the same thing - and works, although I did have the same problem with other methods. To be honest, I have no idea how I managed to solve it on the other ones 😅; I tried to change it to be almost the same but it still doesn't work.