def _combine_indexers(indexers1, indexers2):
    """ Conbine index data from two indexers
    :param indexers1: list of indexers to combine index data
    :param indexers2: second list of indexers to combine index data
    :return: first list of indexers containing index data from both indexers in pair"""
    if len(indexers1) != len(indexers2):
        raise ValueError('Cannot reduce results with different dimensions')

    return [indexer_pair[0] + indexer_pair[1] for indexer_pair in zip(indexers1, indexers2)]
 Conbine index data from two indexers
    :param indexers1: list of indexers to combine index data
    :param indexers2: second list of indexers to combine index data
    :return: first list of indexers containing index data from both indexers in pair
petastorm/etl/rowgroup_indexing.py