@Nullable
  public synchronized List<ProducerContextCallbacks> setIsPrefetchNoCallbacks(boolean isPrefetch) {
    if (isPrefetch == mIsPrefetch) {
      return null;
    }
    this.mIsPrefetch = isPrefetch;
    return new ArrayList<>(mCallbacks);
  }
Changes isPrefetch property.

<p>This method does not call any callbacks. Instead, caller of this method is responsible for
iterating over returned list and calling appropriate method on each callback object. {@see
#callOnIsPrefetchChanged}

@return list of callbacks if the value actually changes, null otherwise
imagepipeline/src/main/java/com/facebook/imagepipeline/producers/BaseProducerContext.java