code: public Opinion newOpinion() {
  	String newId = idManager.getNextId(AnnotationType.OPINION);
  	Opinion newOpinion = new Opinion(newId);
  	annotationContainer.add(newOpinion, Layer.OPINIONS, AnnotationType.OPINION);
  	return newOpinion;
      }
docs: Creates a new opinion object. It assigns an appropriate ID to it. The opinion is added to the document.
  @return a new opinion.