How to integrate bootstrap and django-ckeditor?

Question

Django

Once upon a time, they simply wrote articles on the site, using the usual functionality of ckeditor. Now a problem arose, since it was already necessary to write separate pages for the site (flatpages). We used bootstrap, but manually adding its classes to different containers is too long. How can bootstrap be integrated with skeditor? I looked at different plugins, but they are paid. Is there another way to do this?
N1ED didn't help either. How can I simply "connect" it to ckeditor?