Closures have been converted into classes with one method. They have been regrouped in modules called methods.py. Only methods modules are cythonized.

Cythonization is made by generating a pyx file from the Python file. This approach doesn't require much adaptation to the Python code. Also, it allows optimizations like dynamic dispatch conversion to switch (Python code would have been dirty to with a lot of if-chains).

As constraints validation has been completely refactored to be cythonized too, error customization has been added at the same time as it was simpler.