docs: public static Iterator<ImmutableRoaringBitmap> convertToImmutable(
        final Iterator<MutableRoaringBitmap> i) {
      return new Iterator<ImmutableRoaringBitmap>() {
  
        @Override
        public boolean hasNext() {
          return i.hasNext();
        }
  
        @Override
        public ImmutableRoaringBitmap next() {
          return i.next();
        }
  
        @Override
        public void remove() {};
  
      };
  
    }