def METHOD_NAME(self):
    """ return specific list cache key based on list last_update object """
    last_update = self.get_queryset().model.last_update_and_count.get('last_update')
    last_update_trek = Trek.last_update_and_count.get('last_update')
    last_update_touristic_content = TouristicContent.last_update_and_count.get('last_update')
    last_update_touristic_event = TouristicEvent.last_update_and_count.get('last_update')
    last_updates = [
        last_update.isoformat() if last_update else '0000-00-00',
        last_update_trek.isoformat() if last_update_trek else '0000-00-00',
        last_update_touristic_content.isoformat() if last_update_touristic_content else '0000-00-00',
        last_update_touristic_event.isoformat() if last_update_touristic_event else '0000-00-00',
    ]
    if 'geotrek.outdoor' in settings.INSTALLED_APPS:
        from geotrek.outdoor.models import Site
        list_update_site = Site.last_update_and_count.get('last_update')
        last_updates.append(
            list_update_site.isoformat() if list_update_site else '0000-00-00',
        )
    last_update = max(*last_updates)
    return f"{self.get_base_cache_string()}:{last_update}"