我有以下型号:
class Person(models.Model):
# fields
class Teacher(Person):
# fields
class Student(Person):
# fields
teacher = models.ForeignKey(teacher)
class Staff(Person):
# fields
class SomeModel(models.Model):
# fields
point_person = models.ForeignKey(Person)
但我想将我的“point_person”仅限于教师和学生。我怎样才能做到这一点?