How to use the prophet.data.YahooCloseData function in prophet

from eventstudy import OrderGenerator


# Based on Homework #7 for Computational Investing
# http://wiki.quantsoftware.org/index.php?title=CompInvesti_Homework_7
# Here we use 2 symbols and a benchmark to reduce data pulled
# but you can use the full sp5002012.txt file from QSTK
# You will have to adjust the portfolio analyzers
# The homework solution's analyzers start the analysis
# when the first trade is conducted instead of the entire
# duration of the backtest.
prophet = Prophet()
symbols = ["AAPL", "XOM", "SPX"]
prophet.set_universe(symbols)

prophet.register_data_generators(YahooCloseData(),
                                 BollingerData(),
                                 BollingerEventStudy())
prophet.set_order_generator(OrderGenerator())
backtest = prophet.run_backtest(start=dt.datetime(2008, 1, 1),
                                end=dt.datetime(2009, 12, 31), lookback=20)

prophet.register_portfolio_analyzers(default_analyzers)
analysis = prophet.analyze_backtest(backtest)
print(analysis)
# +----------------------------------------+
# | sharpe            |    -0.851247401074 |
# | average_return    | -2.04368321273e-07 |
# | cumulative_return |          -0.000103 |
# | volatility        |  3.81116761073e-06 |
# +----------------------------------------+

def __init__(self, cache_path=None, data_path=None):
        super(YahooCloseData, self).__init__(cache_path=cache_path,
                                             data_path=data_path)