How does GenericCSVData work?

[dlscodes]

Hi everyone, while I'm studying Backtrader's DataFeed, I encountered a confused question about GenericCSVData. Please tell me what am I doing wrong? Thanks to everyone.

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)
import datetime 
import backtrader as bt


class TestStrategy(bt.Strategy):
    params = (
        ('maperiod', 2),
    )

    def log(self, txt, dt=None):
        ''' Logging function fot this strategy'''
        dt = dt or self.datas[0].datetime.date(0)
        print('%s, %s' % (dt.isoformat(), txt))
        
    def __init__(self):
        self.dataclose = self.datas[0].close
        self.sma = bt.indicators.MovingAverageSimple(self.datas[0], period=self.params.maperiod)
        self.sma2 = bt.indicators.MovingAverageSimple(self.datas[0], period=self.params.maperiod * 2)

    def prenext(self):
        self.log("in prenex, len:%s" % len(self))

    def notify_order(self, order):
        self.log("In Order, order status: %s" % order.status)

    def notify_trade(self, trade):
        self.log("In trade, %s" % str(trade))

    def nextstart(self):
        self.log("nextstart called , len=%s" % len(self))
        super(TestStrategy, self).nextstart()

    def next(self):
        # Simply log the closing price of the series from the reference
        self.log('Close, %.2f' % self.dataclose[0])


if __name__ == '__main__':
    cerebro = bt.Cerebro()
    data = bt.feeds.GenericCSVData(
        dataname='datas/orcl-1995-2014.txt',
        fromdate=datetime.datetime(1995, 1, 1),
        todate=datetime.datetime(1955, 12, 31),
        dtformat='%Y-%m-%d',
        datetime=0,
        time=-1,
        high=1,
        low=2,
        open=3,
        close=4,
        volume=5,
        openinterest=6,
        timeframe=bt.TimeFrame.Days
    )
    cerebro.adddata(data)
    cerebro.addstrategy(TestStrategy)
    print('Starting Portfolio Value: %.2f' % cerebro.broker.getvalue())
    cerebro.run()
    print('Final Portfolio Value: %.2f' % cerebro.broker.getvalue())

When i run the code， some errors happened as follow:

File "D:\ProgramData\Anaconda3\envs\python36\lib\site-packages\backtrader\indicators\basicops.py", line 364, in once
    dst[i] = math.fsum(src[i - period + 1:i + 1]) / period
IndexError: array assignment index out of range

[dlscodes]

Sorry, it's a stupid question. I found that i set a wrong todate in instantiating GenericCSVData. Because the todate is earlier thanfromdate.