def get_shock_sds_index_tuples(periods, factors):
    """Index tuples for shock_sd.

    Args:
        periods (list): The periods of the model.
        factors (list): The latent factors of the model.

    Returns:
        ind_tups (list)

    """
    ind_tups = []
    for period in periods[:-1]:
        for factor in factors:
            ind_tups.append(("shock_sds", period, factor, "-"))
    return ind_tups