如何标注Django查询的天数计算？

from django.db import models
from datetime import datetime, timedelta

class MyModel(models.Model):
    start_date = models.DateField()
    end_date = models.DateField()

    @property
    def duration_in_days(self):
        duration = self.end_date - self.start_date
        return duration.days

from datetime import date

# 获取持续天数大于等于7天的记录
my_objects = MyModel.objects.filter(duration_in_days__gte=7)

# 按持续天数降序排序
my_objects = MyModel.objects.order_by('-duration_in_days')