code: static Optional<AnnotatedBeanFactory<?>> find(@Nullable BeanFactoryId beanFactoryId) {
          if (beanFactoryId == null) {
              return Optional.empty();
          }
          final AnnotatedBeanFactory<?> factory = factories.get(beanFactoryId);
          return factory != null && factory != unsupportedBeanFactory ? Optional.of(factory)
                                                                      : Optional.empty();
      }
docs: Returns a factory of the specified {@link BeanFactoryId}.