code: @Override
      public void build(final int layer, final List<WordFrequency> wordFrequencies) {
          final Future<?> completionFuture = executorservice.submit(() -> {
              LOGGER.info("Starting to build WordCloud Layer {} in new Thread", layer);
              super.build(layer, wordFrequencies);
          });
  
          executorFutures.add(completionFuture);
      }
docs: constructs the wordcloud specified by layer using the given
  wordfrequencies.<br>
  This is a non-blocking call.
  
  @param layer
  Wordcloud Layer
  @param wordFrequencies
  the WordFrequencies to use as input