code: func (s *rowSegment) Shift() (*rowSegment, error) {
  	//TODO deal with overflow
  	data, err := s.data.Shift(1)
  	if err != nil {
  		return nil, errors.Wrap(err, "shifting roaring data")
  	}
  
  	return &rowSegment{
  		data:  *data,
  		shard: s.shard,
  		n:     data.Count(),
  	}, nil
  }
docs: // Shift returns s shifted by 1 bit.