docs: @Override
      public void addNearestNeighbours(@Nonnull Element element) {
          if (element == null) {
              throw new IllegalArgumentException("An element must be specified.");
          }
  
          if (element instanceof Person || element instanceof SoftwareSystem) {
              super.addNearestNeighbours(element, Person.class);
              super.addNearestNeighbours(element, SoftwareSystem.class);
          } else {
              throw new IllegalArgumentException("A person or software system must be specified.");
          }
      }