code: public DataSource<CloseableReference<CloseableImage>> fetchDecodedImage(
        ImageRequest imageRequest,
        Object callerContext) {
      return fetchDecodedImage(imageRequest, callerContext, ImageRequest.RequestLevel.FULL_FETCH);
    }
docs: Submits a request for execution and returns a DataSource representing the pending decoded
  image(s).
  <p>The returned DataSource must be closed once the client has finished with it.
  
  @param imageRequest the request to submit
  @param callerContext the caller context for image request
  @return a DataSource representing the pending decoded image(s)