code: func (s *rowSegment) Difference(other *rowSegment) *rowSegment {
  	data := s.data.Difference(&other.data)
  
  	return &rowSegment{
  		data:  *data,
  		shard: s.shard,
  		n:     data.Count(),
  	}
  }
docs: // Difference returns the diff of s and other.