default ReplacementOccurred firstTimeOnly(){
  ReplacementOccurred delegate=this;
  Set<String> alreadySeen=Collections.newSetFromMap(new ConcurrentHashMap<>());
  Map<String,String> originalByReplacement=new ConcurrentHashMap<>();
  return null;
}

default ReplacementOccurred firstTimeOnly ( ) { ReplacementOccurred delegate = this ; Set < String > alreadySeen = Collections . newSetFromMap ( new ConcurrentHashMap < > ( ) ) ; Map < String , String > originalByReplacement = new ConcurrentHashMap < > ( ) ; return null ; }
create a new function that calls this function only the first time it sees each unique original , and ignores subsequent calls for originals it has already seen .
