static <K extends @Nullable Object, V1 extends @Nullable Object, V2 extends @Nullable Object>
      EntryTransformer<K, V1, V2> asEntryTransformer(final Function<? super V1, V2> function) {
    checkNotNull(function);
    return new EntryTransformer<K, V1, V2>() {
      @Override
      @ParametricNullness
      public V2 transformEntry(@ParametricNullness K key, @ParametricNullness V1 value) {