django：tastypie REST框架脱水问题

Question

在我的模型中，我有金额字段，我想要总和金额。

遵循我的模型;的 model.py

class EntityLoan(models.Model):
    id = models.BigIntegerField(primary_key=True)
    amount = models.FloatField(blank=True, null=True)
    status = models.ForeignKey('StaticStatus',db_column='status',related_name='+status+')
    start_date = models.DateTimeField(blank=True, null=True)
    end_date = models.DateTimeField(blank=True, null=True)
    last_modified_by = models.ForeignKey('EntityUser', db_column='last_modified_by')
    last_modified_date = models.DateTimeField()
    class Meta:
        db_table = 'entity_loan'

以下是我的tastypie资源代码 api.py

 class LoanResource(ModelResource): 

            class Meta:
                queryset = EntityLoan.objects.all()
                resource_name = 'entityloan'
                fields = ['amount']
                filtering = {
                    'amount': ALL,

                }       
            def determine_format(self, request):
                return 'application/json'
            def dehydrate(self,bundle):
                items= bundle.obj.amount.all()
                bundle.data['item_count']=items.Sum('amount')
                bundle.data['items'] = [i.to_dict() for i in items]
                return bundle

但我收到错误

  

error_message“：”'float'对象没有属性'all'“，