code: protected void addExtendsImplements(TypeElement parent, TypeElement typeElement,
              Content contentTree) {
          SortedSet<TypeElement> interfaces = new TreeSet<>(utils.makeGeneralPurposeComparator());
          typeElement.getInterfaces().stream().forEach((t) -> {
              interfaces.add(utils.asTypeElement(t));
          }
docs: Add information regarding the classes which this class extends or
  implements.
  
  @param parent the parent class of the class being documented
  @param typeElement the TypeElement under consideration
  @param contentTree the content tree to which the information will be added