code: func (skv *sortableKeyvals) Swap(i, j int) {
  	keyIdx, keyJdx := i*2, j*2
  	valIdx, valJdx := keyIdx+1, keyJdx+1
  	keyI, valI := skv.keyvals[keyIdx], skv.keyvals[valIdx]
  	skv.keyvals[keyIdx], skv.keyvals[valIdx] = skv.keyvals[keyJdx], skv.keyvals[valJdx]
  	skv.keyvals[keyJdx], skv.keyvals[valJdx] = keyI, valI
  }
docs: // Swap swaps the elements with indexes i and j.