def _download(url, path, md5sum=None):
    """
    Download from url, save to path.
    url (str): download url
    path (str): download to given path
    """
    if not osp.exists(path):
        os.makedirs(path)

    fname = osp.split(url)[-1]
    fullname = osp.join(path, fname)
    retry_cnt = 0
    while not (osp.exists(fullname) and _check_exist_file_md5(fullname, md5sum,
                                                              url)):
        if retry_cnt < DOWNLOAD_RETRY_LIMIT:
            retry_cnt += 1
        else:
            raise RuntimeError("Download from {} failed. "
                               "Retry limit reached".format(url))

        # NOTE: windows path join may incur \, which is invalid in url
        if sys.platform == "win32":
            url = url.replace('\\', '/')

        req = requests.get(url, stream=True)
        if req.status_code != 200:
            raise RuntimeError("Downloading from {} failed with code "
                               "{}!".format(url, req.status_code))

        # For protecting download interupted, download to
        # tmp_fullname firstly, move tmp_fullname to fullname
        # after download finished
        tmp_fullname = fullname + "_tmp"
        total_size = req.headers.get('content-length')
        with open(tmp_fullname, 'wb') as f:
            if total_size:
                for chunk in tqdm.tqdm(
                        req.iter_content(chunk_size=1024),
                        total=(int(total_size) + 1023) // 1024,
                        unit='KB'):
                    f.write(chunk)
            else:
                for chunk in req.iter_content(chunk_size=1024):
                    if chunk:
                        f.write(chunk)
        shutil.move(tmp_fullname, fullname)
    return fullname

    Download from url, save to path.
    url (str): download url
    path (str): download to given path
    
deploy/pipeline/download.py