Python 3.9 is now generally available.

google.appengine.api.images.delete_serving_url

Deletes a serving URL created for blob_key using get_serving_url.

blob_key The BlobKey, BlobInfo, string, or Unicode representation of the BlobKey of a blob with an existing URL that you want to delete.
rpc Optional UserRPC object.

BlobKeyRequiredError If no blob_key was specified.
InvalidBlobKeyError If the blob_key supplied was invalid.
Error There was a generic error deleting the serving URL.