def create_list(devkit_dir, years, output_dir):
    """
    create following list:
        1. trainval.txt
        2. test.txt
    """
    trainval_list = []
    test_list = []
    for year in years:
        trainval, test = _walk_voc_dir(devkit_dir, year, output_dir)
        trainval_list.extend(trainval)
        test_list.extend(test)

    random.shuffle(trainval_list)
    with open(osp.join(output_dir, 'trainval.txt'), 'w') as ftrainval:
        for item in trainval_list:
            ftrainval.write(item[0] + ' ' + item[1] + '\n')

    with open(osp.join(output_dir, 'test.txt'), 'w') as fval:
        ct = 0
        for item in test_list:
            ct += 1
            fval.write(item[0] + ' ' + item[1] + '\n')

    create following list:
        1. trainval.txt
        2. test.txt
    
ppdet/utils/voc_utils.py