ListSerializer对象不可迭代

Question

我有一个约为door和door_group s的权限模型。

door和door_group模型之间存在ManyToMany关系。他们与permission的OneToMany相关。

我想问一下，我怎样才能获得所有door特定的不同权限？

    permissions_list = []                                                                                                                       
    permissions_list.append(door.permission_set.all()) 
    for group in door.door_group_set.all():            
      permissions_list.append(group.permission_set.all()) 

    serializer = PermissionSerializer(permissions_list, many=True)         

    return Response(serializer.data)

我获得了所有权限，但我无法使用ModelSerializer类序列化它。

权限模型：

class Permission(models.Model):                                                                                                                       
    user = models.ForeignKey('users.EmailUser')                                                                                                       
    door = models.ForeignKey('doors.Door', null=True, blank=True)                                                                                     
    door_group = models.ForeignKey('doors.Door_group', null=True, blank=True)                                                                         
    days = models.CharField(validators=[validate_comma_separated_integer_list], max_length=13, null=True)                                             
    start_hour = models.TimeField(default='00:00')                                                                                                    
    end_hour = models.TimeField(default='00:00')                                                                                                      
    created_date = models.DateTimeField(default=timezone.now)                                                                                         
    updated_date = models.DateTimeField(auto_now=True)                                                                                                

    def __unicode__(self):                                                                                                                            

        return 'Days: ' + self.days + ' Start:' + str(self.start_hour) + ' End: ' + str(self.end_hour) + ' User: '+ self.user.username                

    def clean(self):                                                                                                                                  
        # Don't allow draft entries to have a pub_date.                                                                                               
        if self.door_group is not None and self.door is not None:                                                                                     
            raise ValidationError('Choose between, group of doors or one door to give permission. Can not choosable both.')                           
        if self.door_group is None and self.door is None:                                                                                             
            raise ValidationError('Choose between, group of doors or one door to give permission.')