def unlist(list_thing, complain=True):
    """transforms [Something] -> Something. By default, raises a ValueError for
    any other list values."""
    if complain and len(list_thing) > 1:
        raise ValueError('More than one element in {}'.format(list_thing))
    elif len(list_thing) == 1:
        return list_thing[0]
    if complain:
        raise ValueError('Nothing in {}'.format(list_thing))
    return None
