使用直通表的不同类型之间的多对多关系

Question

我一直在努力了解如何让多对多关系正常运作。这是实体和事件的简化模型。我试图建模的关系是：

• 实体与其他实体有多对多
• 实体有多对多的事件

从查找角度来看，到目前为止这是有效的：

• 查找与
有一对多关系的实体
• 查找与此实体有关系的实体（反向/向后关系）
• 查找与
有一对多关系的事件

但我无法弄明白：

• 查找与此事件有关系的实体（反向/向后关系）

  class Entity2EntityRel(Model):
      from_entity = ForeignKey('Entity', to_field='uuid',
                               related_name="from_entity")
      to_entity = ForeignKey('Entity', to_field='uuid',
                             related_name="to_entity")
      relation = CharField(max_length=64)
  
      def __unicode__(self):
          return json.dumps({
              "from_entity": str(self.from_entity),
              "relation": str(self.relation),
              "to_entity": str(self.to_event)
          })
  
  
  class Entity2EventRel(Model):
      from_entity = ForeignKey('Entity', to_field='uuid',
                               related_name="from_entity_ev")
      to_event = ForeignKey('Event', to_field='uuid',
                            related_name="to_event_en")
      relation = CharField(max_length=64)
  
      def __unicode__(self):
          return json.dumps({
              "from_entity": str(self.from_entity),
              "relation": str(self.relation),
              "to_event": str(self.to_event)
          })
  
  
  
  
  class Entity(PolymorphicModel):
      uuid = UUIDField(unique=True)
      name = CharField(max_length=255, unique=True)
      entity_rels = ManyToManyField(
          'Entity',
          through='Entity2EntityRel',
          related_name="related_entity_set",
          symmetrical=False)
      event_rels = ManyToManyField(
          'Event',
          through='Entity2EventRel',
          related_name="related_event_set",
          symmetrical=False)
  
      def add_entity_rel(self, entity, relation_name):
          relationship, created = Entity2EntityRel.objects.get_or_create(
              from_entity=self,
              to_entity=entity,
              relation=relation_name)
          return relationship
  
      # return entities related to me
      def get_entity_rels(self, relation_name):
          return self.entity_rels.filter(
              to_entity__relation=relation_name,
              to_entity__from_entity=self)
  
      # return items that have a relation to me
      def get_related_entities(self, relation_name):
          return self.related_entity_set.filter(
              from_entity__relation=relation_name,
              from_entity__to_entity=self)
  
      def add_event_rel(self, event, relation_name):
          relationship, created = Entity2EventRel.objects.get_or_create(
              from_entity=self,
              to_event=event,
              relation=relation_name)
          return relationship
  
      # return events related to me
      def get_event_rels(self, relation_name):
          return self.event_rels.filter(
              to_event_en__relation=relation_name,
              to_event_en__from_entity=self)
  

现在我如何获得与特定事件相关的实体？