public static FeatureExtractor<IString,String> factory(String featurizerName,boolean withGaps,String... featurizerSpecs){
  return factory(featurizerName,withGaps,null,featurizerSpecs);
}

public static FeatureExtractor < IString , String > factory ( String featurizerName , boolean withGaps , String ... featurizerSpecs ) { return factory ( featurizerName , withGaps , null , featurizerSpecs ) ; }
get a feature extractor .
