我正在学习Django，想要检索所有与我正在查看的对象不有关系的对象。
这个想法是一个简单的Twitter模仿者。
我正在尝试弄清楚如何实现get_non_followers。

from django.db import models

RELATIONSHIP_FOLLOWING = 1
RELATIONSHIP_BLOCKED = 2
RELATIONSHIP_STATUSES = (
                         (RELATIONSHIP_FOLLOWING, 'Following'),
                         (RELATIONSHIP_BLOCKED, 'Blocked'),
)


class UserProfile(models.Model):
    name = models.CharField(max_length=200)
    website = models.CharField(max_length=200)
    email = models.EmailField()
    relationships = models.ManyToManyField('self', through='Relationship', 
                                           symmetrical=False, 
                                           related_name='related_to')
    def __unicode__ (self):
        return self.name
    
    def add_relationship(self, person, status):
        relationship, created = Relationship.objects.get_or_create(
            from_person=self,
            to_person=person,
            status=status)
        return relationship
    
    def remove_relationship(self, person, status):
        Relationship.objects.filter(
            from_person=self, 
            to_person=person,
            status=status).delete()
        return
       

    def get_relationships(self, status):
        return self.relationships.filter(
        to_people__status=status, 
        to_people__from_person=self)
        
    
    def get_related_to(self, status):
        return self.related_to.filter(
            from_people__status=status, 
            from_people__to_person=self)
    
    def get_following(self):
        return self.get_relationships(RELATIONSHIP_FOLLOWING)
    
    def get_followers(self):
        return self.get_related_to(RELATIONSHIP_FOLLOWING)

    def get_non_followers(self):
        # How to do this?
        return

class Relationship(models.Model):
    from_person = models.ForeignKey(UserProfile, related_name='from_people')
    to_person = models.ForeignKey(UserProfile, related_name='to_people')
    status = models.IntegerField(choices=RELATIONSHIP_STATUSES)