@Nullable
  @Override
  public <E> E getExtra(String key, @Nullable E valueIfNotFound) {
    Object maybeValue = mExtras.get(key);
    if (maybeValue == null) {
      return valueIfNotFound;
    }
    //noinspection unchecked
    return (E) maybeValue;
  }
Calls {@code onPriorityChanged} on each element of the list. Does nothing if list == null
imagepipeline/src/main/java/com/facebook/imagepipeline/producers/BaseProducerContext.java