from django.db.models.query import Prefetch
from django.dispatch import Signal
from django.urls import reverse
from django.db.models.query import Prefetch
from django.dispatch import Signal
from django.urls import reverse
created_at = models.DateTimeField(_('creation date'), auto_now_add=True, db_index=True)
changed_at = models.DateTimeField(_('creation date'), auto_now=True, db_index=True)
created_at = models.DateTimeField(_('creation date'), auto_now_add=True, db_index=True)
changed_at = models.DateTimeField(_('creation date'), auto_now=True, db_index=True)