Pandas extend datafeeds error

[羅成浩]

class Mypandas(bt.feeds.PandasData):
    # Add a 'pe' line to the inherited ones from the base class
    lines = ('timestamp',)

    # openinterest in GenericCSVData has index 7 ... add 1
    # add the parameter to the parameters inherited from the base class
    params = (('timestamp', 8),)

data = Mypandas(dataname=df)

# Add the Data Feed to Cerebro
cerebro.adddata(data)

trying to extend one line, but give me a error.