Django覆盖模型保存方法，以检查多对多字段是否已更改

from django.db import models

class MyModel(models.Model):
    m2m_field = models.ManyToManyField(OtherModel)

    def save_with_check(self, *args, **kwargs):
        # 调用父类的保存方法
        super().save(*args, **kwargs)

        # 检查多对多字段是否发生了变化
        if self.pk:
            old_instance = MyModel.objects.get(pk=self.pk)
            if self.m2m_field.all() != old_instance.m2m_field.all():
                # 多对多字段发生了变化，执行相应的操作
                # ...

    def save(self, *args, **kwargs):
        self.save_with_check(*args, **kwargs)