def get_index_lists(partition_columns):
    """
    Find lists of indices for partition_ids level-sets

    :param partition_columns: non-empty list of lists of list of hashables/comparables
    :return: dictionary of index lists for each level-set of the keys
    """
    index_lists = {}
    for i in range(len(partition_columns[0])):
        pi = []
        for j in range(len(partition_columns)):
            pi.append(partition_columns[j][i])
        pi = tuple(pi)
        try:
            lst = index_lists[pi]
        except KeyError:
            lst = []
            index_lists[pi] = lst
        lst.append(i)
    return index_lists
