docs: private static DefaultListableBeanFactory buildListableBeanFactory(Map<String, ?> extraBeans) {
          //new empty context
          final DefaultListableBeanFactory parentBeanFactory = new DefaultListableBeanFactory();  
          
          //Injection of the new beans in the context
          for (String key : extraBeans.keySet()) {
              parentBeanFactory.registerSingleton(key, extraBeans.get(key));
          }
          return parentBeanFactory;
      }