code: public static Set<String> parsePropertyAttribute(AnnotationMirror annotation) {
      assert getName(annotation.getAnnotationType().asElement()).equals("Property");
      String attributesStr = (String) getAnnotationValue(annotation, "value");
      Set<String> attributes = new HashSet<>();
      if (attributesStr != null) {
        attributes.addAll(Arrays.asList(attributesStr.split(",\\s*")));
        attributes.remove(""); // Clear any empty strings.
      }
      return attributes;
    }
docs: Returns the attributes of a Property annotation.