@Nullable
  @Override
  // NULLSAFE_FIXME[Inconsistent Subclass Return Annotation]
  public AnimatedImageResult getAnimatedImageResult() {
    return null;
  }
Implementation of {@link AnimatedDrawableBackend} for unit tests.
animated-base/src/test/java/com/facebook/imagepipeline/animated/testing/TestAnimatedDrawableBackend.java