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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def symbol_bollinger(symbol='GOOG', start=datetime.datetime(2008, 1, 1), end=datetime.datetime(2009, 12, 31), price_type='close', cleaner=clean_dataframe, window=20, sigma=1.):
 """Calculate the Bolinger indicator value """

    symbols = normalize_symbols(symbol)
    prices = price_dataframe(symbols, start=start, end=end, price_type=price_type, cleaner=cleaner)
    return series_bollinger(prices[symbols[0]], window=window, sigma=sigma, plot=False)