code: public void wrap(ImmutableRoaringBitmap r) {
      this.roaringBitmap = r;
      this.hs = 0;
      this.pos = (short) (this.roaringBitmap.highLowContainer.size() - 1);
      this.nextContainer();
    }
docs: Prepares a bitmap for iteration
  
  @param r bitmap to be iterated over