docs: private void processNeighbors(DoubleDBIDListIter neighbor, ModifiableDBIDs currentCluster, ArrayModifiableDBIDs seeds) {
      final boolean ismetric = getDistanceFunction().isMetric();
      for(; neighbor.valid(); neighbor.advance()) {
        if(processedIDs.add(neighbor)) {
          if(!ismetric || neighbor.doubleValue() > 0.) {
            seeds.add(neighbor);
          }
        }
        else if(!noise.remove(neighbor)) {
          continue;
        }
        currentCluster.add(neighbor);
      }
    }