docs: protected void checkObserverMethods() {
          Collection<EnhancedAnnotatedMethod<?, ? super T>> observerMethods = BeanMethods.getObserverMethods(this.getEnhancedAnnotated());
          Collection<EnhancedAnnotatedMethod<?, ? super T>> asyncObserverMethods = BeanMethods.getAsyncObserverMethods(this.getEnhancedAnnotated());
          checkObserverMethods(observerMethods);
          checkObserverMethods(asyncObserverMethods);
      }