docs: public List<TopicConfiguration> getTopicConfigurations() {
          List<TopicConfiguration> topicConfigs = new ArrayList<BucketNotificationConfiguration.TopicConfiguration>();
          for (Map.Entry<String, NotificationConfiguration> entry : configurations
                  .entrySet()) {
              if (entry.getValue() instanceof TopicConfiguration) {
                  topicConfigs.add((TopicConfiguration) entry.getValue());
              }
          }
          return topicConfigs;
      }