public List<String> extract(Configuration config){
  List<String> features=new ArrayList<String>();
  for (  Extractor fe : extractors) {
    features.add(fe.extract(config));
  }
  return features;
}

public List < String > extract ( Configuration config ) { List < String > features = new ArrayList < String > ( ) ; for ( Extractor fe : extractors ) { features . add ( fe . extract ( config ) ) ; } return features ; }
extracts all feature from this configuration .
