docs: private void logClusterSizes(String m, int dimensionality, Object2ObjectOpenCustomHashMap<long[], List<ArrayModifiableDBIDs>> clustersMap) {
      if(LOG.isVerbose()) {
        final StringBuilder msg = new StringBuilder(1000).append(m).append('\n');
        for(ObjectIterator<Object2ObjectMap.Entry<long[], List<ArrayModifiableDBIDs>>> iter = clustersMap.object2ObjectEntrySet().fastIterator(); iter.hasNext();) {
          Object2ObjectMap.Entry<long[], List<ArrayModifiableDBIDs>> entry = iter.next();
          msg.append(BitsUtil.toStringLow(entry.getKey(), dimensionality)).append(" sizes:");
          for(ArrayModifiableDBIDs c : entry.getValue()) {
            msg.append(' ').append(c.size());
          }
          msg.append('\n');
        }
        LOG.verbose(msg.toString());
      }
    }