FK filtering in django model hierarchy?

Question

Django

Is it possible, and if possible, please give a small example of how you can filter possible Fk for a model in django with such a hierarchy:
(I don’t quite understand how this can be done through Limit_choices_to using Q () / F ())
Server < - Conf < - s_conf -> < - context
Server < - e_conf < - context
context_FK can only be cat. is in the e_conf model for the same Server for s_conf and e_conf;
Simply put, when creating an s_conf instance, I can only set the context_id for it, cat. is in the e_conf table for the same Server.
Through a form or a view is an option, but I would like it to be automatically validated through the shell and in the code too.