code: public CompletableFuture<List<RuleDescription>> getRulesAsync(String topicName, String subscriptionName) {
          return getRulesAsync(topicName, subscriptionName, 100, 0);
      }
docs: Retrieves the list of rules for a given topic-subscription in the namespace.
  @param topicName - The name of the topic.
  @param subscriptionName - The name of the subscription.
  @return the first 100 rules.