<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parents(args):
 """ %prog parents gffile models.ids Find the parents given a list of IDs in "models.ids". """

    p = OptionParser(parents.__doc__)

    opts, args = p.parse_args(args)

    if len(args) != 2:
        sys.exit(not p.print_help())

    gff_file, idsfile = args
    g = make_index(gff_file)
    fp = open(idsfile)
    for row in fp:
        cid = row.strip()
        b = next(g.parents(cid, 1))
        print("\t".join((cid, b.id)))