docs: private void fillDensities(KNNQuery<O> knnq, DBIDs ids, WritableDoubleDataStore dens) {
      FiniteProgress prog = LOG.isVerbose() ? new FiniteProgress("Densities", ids.size(), LOG) : null;
      for(DBIDIter iter = ids.iter(); iter.valid(); iter.advance()) {
        final KNNList neighbors = knnq.getKNNForDBID(iter, k);
        dens.putDouble(iter, neighbors.getKNNDistance());
        LOG.incrementProcessed(prog);
      }
      LOG.ensureCompleted(prog);
    }