Like max(close,n)

When I use cerebro.optstrategy(...) and cerebro.run(), I got an exception if using some analyzers( PeriodStats, SharpeRatio) ：

File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python37_64\lib\threading.py", line 917, in _bootstrap_inner
self.run()
File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python37_64\lib\threading.py", line 865, in run
self._target(*self._args, **self._kwargs)
File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python37_64\lib\multiprocessing\pool.py", line 470, in _handle_results
task = get()
File "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Python37_64\lib\multiprocessing\connection.py", line 251, in recv
return _ForkingPickler.loads(buf.getbuffer())
AttributeError: Can't get attribute 'Lines_LineSeries_LineIterator_DataAccessor_ObserverBase_Observer_DataTrades_5991202d0983450997d03f799478a7ad' on <module 'backtrader.lineseries' from 'c:\users\kaima\source\repos\PythonHello\PythonHello\env37\lib\site-packages\backtrader\lineseries.py'>