策略提示’Series’ object has no attribute ‘isloc’

Traceback (most recent call last):
  File "d:/TianQin/strategies/学习示例/VS05-double MA.py", line 13, in <module>
    ma = sum(klines.close.isloc[-15:])/15
  File "D:\VN Studio\lib\site-packages\pandas\core\generic.py", line 5057, in __getattr__
    return object.__getattribute__(self, name)
AttributeError: 'Series' object has no attribute 'isloc'
Task was destroyed but it is pending!
task: <Task pending coro=<TqApi._windows_patch() running at D:\VN Studio\lib\site-packages\tqsdk\api.py:1445> wait_for=<Future pending cb=[<TaskWakeupMethWrapper object at 0x000000000B9DC2B8>()]> cb=[TqApi._on_task_done()]>