code: @Override
      public void update(Observable o, Object arg) {
          if (arg instanceof String) {
              lines.add((String) arg);
          }
          if (arg instanceof List<?>) {
              lines.addAll((List<String>) arg);
          }
          if (arg instanceof Exception) {
              Exception e = (Exception) arg;
              PresentationManager.getPm().error(e);
              lines.add(e.getMessage());
          }
      }
docs: Inherited from Observer
  @param o
  @param arg