Django模型对自类的引用

Question

我有一个这样的模型（简化）：

class Project(TimeStampedModel, StartFinishModel):
    project_id = models.CharField(max_length=64)
    budget = models.DecimalField(max_digits=11)

class Task():
   name = models.CharField(max_length=256)
   parent = TreeForeignKey('self',
                            on_delete=models.CASCADE,
                            related_name='children')
   project = models.ForeignKey('prosystem.Project',
                                related_name='tasks',
                                on_delete=models.CASCADE)
  @property
  def current_budget(self):
     # this does not work now
     sumz = self.cls.objects.filter(project = self.project).aggregate(Sum('budget'))
     return sumz

问题是-如何从自己的Task属性中过滤current_budget模型的所有实例？我知道可能会有一些 meta.class < / em>参考，但找不到有关该信息。谢谢您的任何建议。