private static Uri createUriForPartialCacheKey(ImageRequest imageRequest) {
    return imageRequest
        .getSourceUri()
        .buildUpon()
        .appendQueryParameter("fresco_partial", "true")
        .build();
  }
Partial disk cache producer.

<p>This producer looks in the disk cache to see if it holds part of the requested image. If the
image is found, then it is passed to the consumer as a non-final result, but an adjusted request
is still sent further along to request the remainder of the image.

<p>When the final result comes from the input producer, the two parts are stitched back together
and returned as a whole.
imagepipeline/src/main/java/com/facebook/imagepipeline/producers/PartialDiskCacheProducer.java