@Override
    public @Nullable V computeIfPresent(
        K key, BiFunction<? super K, ? super @NonNull V, ? extends @Nullable V> remappingFunction) {
      synchronized (mutex) {
        return delegate().computeIfPresent(key, remappingFunction);
      }
    }

    @Override
    public @Nullable V compute(
        K key,
        BiFunction<? super K, ? super @Nullable V, ? extends @Nullable V> remappingFunction) {