code: func replaceNonAlpha(s string, replace byte) string {
  	byts := []byte(s)
  	newByts := make([]byte, len(byts))
  
  	for i := 0; i < len(byts); i++ {
  		if byts[i] < 'A' || (byts[i] > 'Z' && byts[i] < 'a') || byts[i] > 'z' {
  			newByts[i] = replace
  		} else {
  			newByts[i] = byts[i]
  		}
  	}
  
  	return string(newByts)
  }
docs: // replaceNonAlpha replaces non alphabet characters with the replace byte.