Python requests 库下载文件有点问题

简单代码：

def save_file(self, folder, url):
    if not url:
        return

    filename = url.rsplit("/", 1)[-1]
    path = os.path.join(folder, filename)
    if os.path.exists(path):
        return path

    r = requests.get(url)
    with open(path, 'wb') as f:
        for chunk in r.iter_content(chunk_size=1024):
            if chunk:
                f.write(chunk)
    return path

这个方法下载文件有时候会有问题，会下载不完整，python 也不是特别熟，看不出啥问题呢，请大佬们指教。