如何并行迭代n个列表？

import concurrent.futures

def process_element(element):
    # 这里是处理单个元素的逻辑
    return element * 2

def parallel_iterate(lists):
    with concurrent.futures.ThreadPoolExecutor() as executor:
        # 创建一个Future列表来保存所有任务的结果
        futures = [executor.submit(process_element, element) for sublist in lists for element in sublist]
        
        # 获取所有任务的结果
        results = [future.result() for future in concurrent.futures.as_completed(futures)]
    
    return results

# 示例列表
lists = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

# 并行迭代并打印结果
results = parallel_iterate(lists)
print(results)