def _make_dlist(dall, rep=1):
    """make a list of strings representing the scans to average

    Parameters
    ----------
    dall : list of all good scans
    rep : int, repetition

    Returns
    -------
    dlist : list of lists of int

    """
    dlist = [[] for d in range(rep)]
    for idx in range(rep):
        dlist[idx] = dall[idx::rep]
    return dlist