def get_storage_fields(obj):
    """get_storage_fields will return a subset of storage object
    fields, to be saved as strings with a datastore object.
    """
    fields = {'storage_bucket': obj['bucket'], 'storage_md5Hash': obj[
        'md5Hash'], 'storage_updated': obj['updated'], 'storage_download':
        obj['mediaLink'], 'storage_metadataLink': obj['selfLink'],
        'storage_crc32c': obj['crc32c'], 'storage_etag': obj['etag'],
        'storage_owner': obj['owner']['entity'], 'storage_name': obj['name'
        ], 'storage_id': obj['id'], 'storage_contentType': obj[
        'contentType'], 'storage_size': obj['size']}
    return fields
