docs: private Container toBitmapIfNeeded() {
      int sizeAsRunContainer = RunContainer.serializedSizeInBytes(this.nbrruns);
      int sizeAsBitmapContainer = BitmapContainer.serializedSizeInBytes(0);
      if (sizeAsBitmapContainer > sizeAsRunContainer) {
        return this;
      }
      return toBitmapContainer();
    }