def append_unique(the_list, new_item):
    """
    append the newe_item to the_list, only if it does not exist

    :param the_list:
    :param new_item:
    :return:
    """
    exist = any(new_item == item for item in the_list)
    if not exist:
        the_list.append(new_item)
    return the_list