def s2_index_to_band_id(band_index):
    """s2_index_toBand_id returns the band_id from the band index 

    :param band_index: band index (0-12 inclusive) referencing sensors in ESA's metadata
    :return: band_id for the band_index
    """

    return {
        0: '1', 1: '2', 2: '3', 3: '4', 4: '5', 5: '6', 6: '7',
        7: '8', 8: '8A', 9: '9', 10: '10', 11: '11', 12: '12'
    }[int(band_index)]