code: @Override
    public MetadataTuple<V> computeWithMetadata(K key, BiFunction<? super K, ? super MetadataTuple<V>, ? extends MetadataTuple<V>> remappingFunction) {
      Lock l = writeLock();
      l.lock();
      try {
        return super.computeWithMetadata(key, remappingFunction);
      } finally {
        l.unlock();
      }
    }
docs: /*
  JDK-8-alike metadata methods