A generator function for listing multipart uploads in a bucket.

def multipart_upload_lister(bucket, key_marker='',
                            upload_id_marker='',
                            headers=None):
    """
    A generator function for listing multipart uploads in a bucket.
    """
    more_results = True
    k = None
    while more_results:
        rs = bucket.get_all_multipart_uploads(key_marker=key_marker,
                                              upload_id_marker=upload_id_marker,
                                              headers=headers)
        for k in rs:
            yield k
        key_marker = rs.next_key_marker
        upload_id_marker = rs.next_upload_id_marker
        more_results= rs.is_truncated