docs: private HyperBoundingBox mbr(final int[] entries, final int from, final int to) {
      SpatialEntry first = this.node.getEntry(entries[from]);
      ModifiableHyperBoundingBox mbr = new ModifiableHyperBoundingBox(first);
      for(int i = from + 1; i < to; i++) {
        mbr.extend(this.node.getEntry(entries[i]));
      }
      return mbr;
    }