docs: private MappeableContainer toBitmapIfNeeded() {
      int sizeAsRunContainer = MappeableRunContainer.serializedSizeInBytes(this.nbrruns);
      int sizeAsBitmapContainer = MappeableBitmapContainer.serializedSizeInBytes(0);
      if (sizeAsBitmapContainer > sizeAsRunContainer) {
        return this;
      }
      return toBitmapContainer();
    }