def merge(new_items, into_list):
    """
    Appends items from `new_items` into `into_list`, only if they are not already there.
    :param new_items:
    :param into_list:
    :return:
    """
    at_least_one_added = False
    for item in new_items:
        if item not in into_list:
            into_list.append(item)
            at_least_one_added = True
    return at_least_one_added