def METHOD_NAME(labels):
    """Convert labels into a list of strings
    :returns: List of label strings
    """
    if not isinstance(labels, (tuple, list, set)):
        labels = tuple((labels, ))
    out = set()
    for label in labels:
        if is_label_object(label):
            out.add(api.get_title(label))
        elif label and is_string(label):
            out.add(label)
        else:
            # ignore the rest
            continue
    return tuple(out)