def METHOD_NAME(url_attrs):
    existing_nums = list(map(lambda url: int(url.split('nsslapd-pluginarg')[1]),
                             [i for i, _ in url_attrs.items()]))
    if len(existing_nums) > 0:
        existing_nums.sort()
        full_num_list = list(range(existing_nums[-1]+2))
        if not full_num_list:
            next_num_list = ["0"]
        else:
            next_num_list = list(filter(lambda x: x not in existing_nums, full_num_list))
    else:
        next_num_list = ["0"]
    return next_num_list[0]