docs: protected void linearScanBatchKNN(List<O> objs, List<KNNHeap> heaps) {
      final PrimitiveDistanceFunction<? super O> rawdist = this.rawdist;
      final Relation<? extends O> relation = getRelation();
      final int size = objs.size();
      // Linear scan style KNN.
      for(DBIDIter iter = relation.getDBIDs().iter(); iter.valid(); iter.advance()) {
        O candidate = relation.get(iter);
        for(int index = 0; index < size; index++) {
          final KNNHeap heap = heaps.get(index);
          final double dist = rawdist.distance(objs.get(index), candidate);
          if(dist <= heap.getKNNDistance()) {
            heap.insert(dist, iter);
          }
        }
      }
    }