django-orchestra/orchestra/contrib/websites/apps.py

from django.apps import AppConfig
from django.contrib.contenttypes.fields import GenericRelation

from orchestra.utils import database_ready


class WebsiteConfig(AppConfig):
    name =  'orchestra.contrib.websites'
    
    def ready(self):
        if database_ready():
            from django.contrib.contenttypes.models import ContentType
            from .models import Content
            qset = Content.content_type.field.get_limit_choices_to()
            for ct in ContentType.objects.filter(qset):
                relation = GenericRelation('websites.Content')
                ct.model_class().add_to_class('content_set', relation)