def expand_levels(levels, labels):
    """
    Multiindexes need expanding so that subtitles repeat
    """
    for label, order in zip(levels, labels):
        current = None
        row = []
        for idx in order:
            if current == idx:
                row.append(None)
            else:
                row.append(label[idx])
                current = idx
        yield row
