docs: public boolean postValidateLevel(final Level level, final ContentSpec contentSpec) {
          // Check if the app should be shutdown
          if (isShuttingDown.get()) {
              shutdown.set(true);
              return false;
          }
  
          boolean valid = true;
  
          // Validate the tags
          if (!validateTopicTags(level, level.getTags(false))) {
              valid = false;
          }
  
          // Validate the info topic
          if (level.getInfoTopic() != null) {
              postValidateInfoTopic(level.getInfoTopic(), contentSpec);
          }
  
          // Validate the sub levels and topics
          for (final Node childNode : level.getChildNodes()) {
              if (childNode instanceof Level) {
                  if (!postValidateLevel((Level) childNode, contentSpec)) {
                      valid = false;
                  }
              } else if (childNode instanceof SpecTopic) {
                  if (!postValidateTopic((SpecTopic) childNode, contentSpec)) {
                      valid = false;
                  }
              }
          }
  
          return valid;
      }