How to create a vtu file with a 3D block model with sub-blocks?

Hi gents!

First of all, I would like to apologize for my broken English. I am a mine engineer with a limited background in software programming. Despite this, I have managed to create some Python applications for my personal use. In my line of work as a mine engineer, we commonly utilize a 3D block model to represent mineral deposits. These 3D block models come in two types: regular and with sub-blocks. In the regular model, we use parallelepipeds (blocks) of the same size. On the other hand, the second type involves using parallelepipeds with varying sizes, always contained within their corresponding parent parallelepipeds. I can easily import regular block models into Paraview, or prepare files using vtk in python. The problem is how can I import 3D block models with sub-blocks in Paraview or prepare the file in python using vtk. I use Spyder (with Anaconda).

Thank you in advance!