code: public boolean process(ContentEvent event) {
          // distinguish between ClusteringContentEvent and ClusteringEvaluationContentEvent
          if (event instanceof ClusteringContentEvent) {
              ClusteringContentEvent cce = (ClusteringContentEvent) event;
              outputStream.put(event);
              if (cce.isSample()) {
                  evaluationStream.put(new ClusteringEvaluationContentEvent(null, new DataPoint(cce.getInstance(), numInstances++), cce.isLastEvent()));
              }
          } else if (event instanceof ClusteringEvaluationContentEvent) {
              evaluationStream.put(event);
          }
          return true;
      }
docs: Process event.
  
  @param event
  the event
  @return true, if successful