def to_display_list(pairs, sort_by="key", allow_empty=True):
    dl = DisplayList()
    if isinstance(pairs, basestring):
        pairs = [pairs, pairs]
    for pair in pairs:
        if isinstance(pair, (tuple, list)):
            dl.add(*pair)
        if isinstance(pair, basestring):
            dl.add(*pairs)
            break
    if allow_empty:
        dl.add("", "")
    if sort_by == "key":
        dl = dl.sortedByKey()
    elif sort_by == "value":
        dl = dl.sortedByValue()
    return dl