human
Here's a good function header given the following:
I wrote the below code

    def get_roidb(imdb_name):
        imdb = get_imdb(imdb_name)
        print('Loaded    dataset    `{:s}`    for    training'.format(imdb.name))
        imdb.set_proposal_method(cfg.TRAIN.PROPOSAL_METHOD)
        print('Set    proposal    method:    {:s}'.format(cfg.TRAIN.PROPOSAL_METHOD))
        roidb = get_training_roidb(imdb)
        return roidb
    roidbs = [get_roidb(s) for s in imdb_names.split('+')]
    roidb = roidbs[0]
    if (len(roidbs) > 1):
        for r in roidbs[1:]:
            roidb.extend(r)
        tmp = get_imdb(imdb_names.split('+')[1])
        imdb = datasets.imdb.imdb(imdb_names, tmp.classes)
    else:
        imdb = get_imdb(imdb_names)
    return (imdb, roidb)

What's a good function header?
assistant
#Here's a good function header.

def combined_roidb(imdb_names):