这是我得到的结果：

可以在ModelForm类中使用流动代码:

class Delivery(models.Model):
    user = models.ForeignKey(Customer, on_delete=models.CASCADE, related_name=_("delivery_user"))
    full_name_reciever = models.CharField(_("Reciever Full Name"), max_length=50)
    pickup_address = models.ForeignKey(Address, on_delete=models.CASCADE, related_name=_("pickup_address"))
    destination_address = models.CharField(max_length=250)
    destination_city = models.ForeignKey(City, on_delete=models.CASCADE, related_name=_("delivery_city"))
    destination_post_code = models.CharField(max_length=20)
    operation_date = models.DateField(
        _("desired pickup date"), auto_now=False, auto_now_add=False, blank=False, null=False
    )
    boxes_number = models.PositiveIntegerField(_("Number of Boxes"), default=1)
    boxes_wight = models.PositiveIntegerField(_("Boxes Wight"), default=1)
    boxes_volume = models.PositiveIntegerField(_("Boxes Volume"), default=0)
    document = models.FileField(
        help_text=_("Delivery Documets"),
        verbose_name=_("Delivery Certificates"),
        upload_to="documents/deliveries_documents/",
    )
    invoice = models.BooleanField(_("check if you want an invoice"), default=False)
    created_at = models.DateTimeField(_("Created at"), auto_now_add=True, editable=False)
    updated_at = models.DateTimeField(_("Updated at"), auto_now=True)
    delivery_key = models.CharField(max_length=200)
    billing_status = models.BooleanField(default=False)
    delivery_status = models.BooleanField(default=False)

    class Meta:
        ordering = ("-created_at",)
        verbose_name = _("Delivery")
        verbose_name_plural = _("Deliveries")

    def __str__(self):
        return str(self.created_at)