def bulkMinuteBarsDF(symbol, dates, token='', version=''):
    '''fetch many dates worth of minute-bars for a given symbol'''
    data = bulkMinuteBars(symbol, dates, token, version)
    df = pd.DataFrame(data)
    if df.empty:
        return df
    _toDatetime(df)
    df.set_index(['date', 'minute'], inplace=True)
    return df
fetch many dates worth of minute-bars for a given symbol