如何在Django中使用自定义自动递增字段实例化对象？

from django.db import models

class MyModel(models.Model):
    custom_id = models.BigAutoField(primary_key=True)
    # 其他字段...

from django.db import models

class MyModel(models.Model):
    custom_id = models.BigAutoField(primary_key=True)
    # 其他字段...

    def save(self, *args, **kwargs):
        if not self.custom_id:
            last_object = MyModel.objects.order_by('-custom_id').first()
            if last_object:
                self.custom_id = last_object.custom_id + 1
            else:
                self.custom_id = 1
        super().save(*args, **kwargs)

my_object = MyModel()
my_object.save()