code: public static Set<Label> getLabels(final Collection<Annotation> annotations) {
          return annotations.stream()
                  .flatMap(AnnotationUtils::extractRepeatable)
                  .map(AnnotationUtils::getMarks)
                  .flatMap(Collection::stream)
                  .collect(Collectors.toSet());
      }
docs: Returns labels from given annotations.
  
  @param annotations annotations to analyse.
  @return discovered labels.