code: public DataSource<CloseableReference<PooledByteBuffer>> fetchEncodedImage(
        ImageRequest imageRequest,
        Object callerContext) {
      return fetchEncodedImage(imageRequest, callerContext, null);
    }
docs: Submits a request for execution and returns a DataSource representing the pending encoded
  image(s).
  
  <p> The ResizeOptions in the imageRequest will be ignored for this fetch
  
  <p>The returned DataSource must be closed once the client has finished with it.
  
  @param imageRequest the request to submit
  @return a DataSource representing the pending encoded image(s)