public Set<String> postProcessingFields(){
  Set<String> fields=new LinkedHashSet<>();
  query.forEach(null);
  sort.forEach(null);
  return fields;
}

public Set < String > postProcessingFields ( ) { Set < String > fields = new LinkedHashSet < > ( ) ; query . forEach ( null ) ; sort . forEach ( null ) ; return fields ; }
returns the names of the involved fields when post processing .
