How to use the prophet.generators.YahooData function in prophet

def test_quickstart():
    prophet = Prophet()
    prophet.set_universe(['AAPL', 'XOM'])

    price_generator = YahooData('Adj Close', 'prices', cache_path=CACHE_PATH)
    prophet.register_data_generators(price_generator)
    prophet.set_order_generator(OrderGenerator())
    backtest = prophet.run_backtest(start=datetime(2010, 1, 1),
                                    end=datetime(2014, 11, 21))

    prophet.register_portfolio_analyzers(default_analyzers)
    analysis = prophet.analyze_backtest(backtest)
    assert round(analysis['sharpe'], 10) == 1.0970973495
    assert round(analysis['average_return'], 10) == 0.0010547843
    assert round(analysis['cumulative_return'], 10) == 2.1688171559
    assert round(analysis['volatility'], 10) == 0.0152622562

    today = datetime(2014, 11, 10)
    expected_orders = Orders(Order(symbol='AAPL', shares=100))
    assert prophet.generate_orders(today) == expected_orders

class OrderGenerator(object):

    def run(self, prices, timestamp, cash, **kwargs):
        symbol = "AAPL"
        orders = Orders()
        if (prices.loc[timestamp, symbol] * 100) < cash:
            orders.add_order(symbol, 100)

        return orders


prophet = Prophet()
prophet.set_universe(['AAPL', 'XOM'])

price_generator = YahooData('Adj Close', 'prices')

prophet.register_data_generators(price_generator)
prophet.set_order_generator(OrderGenerator())
backtest = prophet.run_backtest(start=datetime(2010, 1, 1))

prophet.register_portfolio_analyzers(default_analyzers)
analysis = prophet.analyze_backtest(backtest)
print(analysis)
# +--------------------------------------+
# | sharpe            |    1.09754359611 |
# | average_return    | 0.00105478425027 |
# | cumulative_return |         2.168833 |
# | volatility        |  0.0152560508189 |
# +--------------------------------------+

# Generate orders for you to execute today

def run(self,
            data,
            symbols,
            start=datetime(2007, 1, 1),
            end=None,
            lookback=0):
        if not end:
            end = datetime.now()

        symbols_data = super(YahooData, self).run(
            data=data, symbols=symbols, start=start,
            end=end, lookback=lookback, source="yahoo")

        return symbols_data[self._column]