Fix python import paths

[SergioQuijanoRey]

The way we are structuring the code right now, and the way we specify the import paths causes some trouble. When launching the notebook scripts, and when testing, it runs fine. But we are not able to debug the code due to import issues. And also we have done some tricky hacks to make everything work.

A big problem to solve is that we run the code in two different situations:

1. Running code from the root of the project, having ./src/lib and ./src/test below
2. Running a local test with the debugging tool, where our cwd is ./src/test and we have ../lib above