Exception inputs are all NaN if runonce=False

Yacc Don

Here is my code

class UserStockStrategy(bt.Strategy):
    def __init__(self):
        self.ind = bt.talib.LINEARREG_SLOPE(bt.talib.LINEARREG_SLOPE(self.datas[0].close, timeperiod=5), timeperiod=2)  #recursive formula

cerebro = bt.Cerebro(runonce=False)

If runonce is True, everything is ok, and exception raised if runonce is False.
And if inner timeperiod equal to outer timeperiod, it's also fine with runonce=False.

Could anybody help me? Thanks.

Yacc Don

@yacc-don
if inner timeperiod is not equal to outer timeperiod, and runonce=False, the got the following excetption:

  File "/home/user/.local/lib/python3.7/site-packages/backtrader/lineiterator.py", line 347, in nextstart
    self.next()
  File "/home/user/.local/lib/python3.7/site-packages/backtrader/talib.py", line 217, in next
    out = self._tafunc(*narrays, **self.p._getkwargs())
  File "/home/user/.local/lib/python3.7/site-packages/talib/__init__.py", line 27, in wrapper
    return func(*args, **kwargs)
  File "talib/_func.pxi", line 3323, in talib._ta_lib.LINEARREG_SLOPE
  File "talib/_func.pxi", line 68, in talib._ta_lib.check_begidx1
Exception: inputs are all NaN