docs: @Override
    public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
      for (Element element : roundEnv.getElementsAnnotatedWith(BugPattern.class)) {
        gson.toJson(BugPatternInstance.fromElement(element), pw);
        pw.write("\n");
      }
  
      if (roundEnv.processingOver()) {
        // this was the last round, do cleanup
        cleanup();
      }
      return true;
    }