code: public Opinion newOpinion(String id) {
          idManager.updateCounter(AnnotationType.OPINION, id);
  	Opinion newOpinion = new Opinion(id);
  	annotationContainer.add(newOpinion, Layer.OPINIONS, AnnotationType.OPINION);
  	return newOpinion;
      }
docs: Creates a new opinion object. It receives its ID as an argument. The opinion is added to the document.
  @return a new opinion.