code: public void addFeature(FeatureInterface<AbstractSequence<C>, C> feature) {
  		features.add(feature);
  		ArrayList<FeatureInterface<AbstractSequence<C>, C>> featureList = groupedFeatures.get(feature.getType());
  		if (featureList == null) {
  			featureList = new ArrayList<FeatureInterface<AbstractSequence<C>, C>>();
  			groupedFeatures.put(feature.getType(), featureList);
  		}
  		featureList.add(feature);
  		Collections.sort(features, AbstractFeature.LOCATION_LENGTH);
  		Collections.sort(featureList, AbstractFeature.LOCATION_LENGTH);
  	}
docs: Add a feature to this sequence. The feature will be added to the collection where the order is start position and if more than
  one feature at the same start position then longest is added first. This helps on doing feature layout for displaying features
  in SequenceFeaturePanel
  @param feature