code: func (s *Sorter) Swap(i, j int) {
  	x := s.Slice.Index(i)
  	y := s.Slice.Index(j)
  	tmp := reflect.New(s.itemType).Elem()
  	tmp.Set(x)
  	x.Set(y)
  	y.Set(tmp)
  }
docs: // Swaps two indices in the slice being sorted.