docs: public static <II extends ImageGray<II>>
  	FastHessianFeatureDetector<II> fastHessian( @Nullable ConfigFastHessian config ) {
  
  		if( config == null )
  			config = new ConfigFastHessian();
  		config.checkValidity();
  
  		// ignore border is overwritten by Fast Hessian at detection time
  		NonMaxSuppression extractor = FactoryFeatureExtractor.nonmax(
  				new ConfigExtract(config.extractRadius, config.detectThreshold, 0, true));
  		return new FastHessianFeatureDetector<>(extractor, config.maxFeaturesPerScale,
  				config.initialSampleSize, config.initialSize, config.numberScalesPerOctave,
  				config.numberOfOctaves, config.scaleStepSize);
  	}