code: func (s StringGroupedNumberPostfixSorter) Less(i, j int) bool {
  	bi, ni := StringSplitNumberPostfix(s[i])
  	bj, nj := StringSplitNumberPostfix(s[j])
  
  	if bi == bj {
  		if len(ni) == len(nj) {
  			inti, _ := strconv.Atoi(ni)
  			intj, _ := strconv.Atoi(nj)
  			return inti < intj
  		} else {
  			return len(ni) < len(nj)
  		}
  	}
  
  	return bi < bj
  }
docs: // Less reports whether the element with
  // index i should sort before the element with index j.