def save_image(self, image, local_filename):
        """
        *Experimental:* Copies an image from Docker to a local tar file. For details, see
        :meth:`docker.client.Client.get_image`.

        :param image: Image name or id.
        :type image: unicode | str
        :param local_filename: Local file to store image into. Will be overwritten if present.
        :type local_filename: unicode | str
        """
        raw = self.get_image(image)
        with open(local_filename, 'wb+') as f:
            for buf in raw:
                f.write(buf)