text: from django.db.models.signals import pre_save
  from django.dispatch import receiver
  
  from address.models import Address
  
  
  @receiver(pre_save, sender=Address)
  def populate_formatted(sender, instance, **kwargs):
      """If "formatted" is empty try to construct it from other values."""
      if not instance.formatted:
          instance.formatted = str(instance)
  