vector<const AnnotationClass*> ann_classes() const;
vector<AnnotationClass*> ann_classes();
AnnotationClass* get_ann_class_by_id(size_t id);
vector<const AnnotationClass*> ann_classes() const;
vector<AnnotationClass*> ann_classes();
AnnotationClass* get_ann_class_by_id(size_t id);