code: List<List<Annotation>> getSentences(AnnotationType type, String groupID) {
  	List<List<Annotation>> sentences = new ArrayList<List<Annotation>>();
  	for (int sent : Helper.getIndexKeys(type, groupID, this.sentIndex)) {
  	    sentences.add(this.getSentAnnotations(sent, type));
  	}
  	return sentences;
      }
docs: Return all annotations of type "type" classified into sentences