Dye: clean up the code

* Ensure the code is PEP8-compliant (with the maximum number of characters per line upped to 100).
* For docstrings it's ok (if necasary) to go over this limit; just make sure to mark the respective docstring with the [``# noqa``](https://stackoverflow.com/questions/45346575/what-does-noqa-mean-in-python-comments) comment (_i.e._ "no quality assurance").
