Python 通过ManyToMany字段与Through在Django Admin中过滤

我的models.py:

class Subject(models.Model):
    name = models.CharField(max_length=200)

class Person(models.Model):
    subject = models.ForeignKey(Subject, on_delete=models.CASCADE, blank=True, null=True)
    school = models.ForeignKey(School, on_delete=models.CASCADE, blank=True, null=True)

class PersonRole(models.Model):
    project = models.ForeignKey('Project', on_delete=models.CASCADE)
    person = models.ForeignKey(Person, on_delete=models.CASCADE)

class Project(models.Model):

    title = models.CharField(max_length=200)
    person = models.ManyToManyField(Person, through=PersonRole)

现在，在我的管理后端，我想添加一个很好的过滤与list_filter.这个过滤器应该可以通过学校过滤一个人是附属于一个项目.换句话说，如果John(属于学校"1号")被附加到项目3号，我希望后端的项目表只显示项目3号. 我想我应该定制一个simplelistfilter.首先，虽然，我有点卡住如何获得附属于项目的人员的学校名单.

目前为止，我的try 是:

class PersonRole(models.Model):

    [...]

    def get_school(self):
        return self.person.school


class Project(models.Model):

    @admin.display(description='PI School')
    def get_PI_school(self):
        return [p for p in self.person.get_school()] 

admin.py:

class ProjectAdmin(admin.ModelAdmin):
    list_display = ("get_PI_school",) #This is just to see if the field is populated

有了这个，我得到'ManyRelatedManager' object has no attribute 'get_school'.