请写一个用python3.x pool.map多进程下载文件的示例代码

import requests
import multiprocessing
def download_file(url):
    local_filename = url.split('/')[-1]
    with requests.get(url, stream=True) as r:
        r.raise_for_status()
        with open(local_filename, 'wb') as f:
            for chunk in r.iter_content(chunk_size=8192):
                if chunk:
                    f.write(chunk)
    return local_filename
if __name__ == '__main__':
    urls = ['https://www.cnblogs.com/pu369/p/17221436.html',
            'http://www.zs.gov.cn/attachment/0/402/402310/1931387.pdf',
            'https://mksoftcdnhp.mydown.com/641c0606/c8d7945f45ef80c0f98df9ab11241922/uploadsoft/newsoft/OCR_ocr-tjxz.exe']
    with multiprocessing.Pool(processes=3) as pool:
        result = pool.map(download_file, urls)
    print(result)