how to export container to tar file?

I want to export container to a tar file, and the export API return a generator. I refer to the example code here.

            >>> c = docker.APIClient()
            >>> f = open('./sh_bin.tar', 'wb')
            >>> bits, stat = c.get_archive(container, '/bin/sh')
            >>> print(stat)
            {'name': 'sh', 'size': 1075464, 'mode': 493,
             'mtime': '2018-10-01T15:37:48-07:00', 'linkTarget': ''}
            >>> for chunk in bits:
            ...    f.write(chunk)
            >>> f.close()

And bellow is my code.

cli = docker.from_env(version="auto", timeout=3600).api 
image = cli.export(container="2991b5d0ead6")

temporary_dir = tempfile.mkdtemp()
with open(temporary_dir + "/" + name + ".tar", "wb") as file:
        for chunk in image:
            file.write(chunk)
tarfile = TarFile(temporary_dir + "/" + name + ".tar")
tarfile.extractall(temporary_dir)

But when I try to extract the tar file in the command line, I got message bellow.

$ tar -xvf 2991b5d0ead6.tar                             
tar: This does not look like a tar archive
tar: Exiting with failure status due to previous errors

Can someone help me? Thank you！

Compare the APIClient.export call with the get_archive example in the issue, then reproduce the generated file with the provided Python code and command-line tar extraction. Inspect the Docker API client behavior to determine whether the output should be a valid tar archive; done means the cause is documented or the export path reliably produces an extractable archive.