Python 3.9 is now generally available.

google.appengine.api.images.histogram_async

Calculates the histogram of the given image - async version.

image_data String of the source image data.
rpc An optional UserRPC object.

An UserRPC object.

NotImageError If the supplied image data is not an image.
BadImageError If the supplied image data is corrupt.
LargeImageError If the supplied image data is too large to process.
Error All other errors.