code: public TopicSharedAccessKeysInner regenerateKey(String resourceGroupName, String topicName, String keyName) {
          return regenerateKeyWithServiceResponseAsync(resourceGroupName, topicName, keyName).toBlocking().single().body();
      }
docs: Regenerate key for a topic.
  Regenerate a shared access key for a topic.
  
  @param resourceGroupName The name of the resource group within the user's subscription.
  @param topicName Name of the topic
  @param keyName Key name to regenerate key1 or key2
  @throws IllegalArgumentException thrown if parameters fail the validation
  @throws CloudException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent
  @return the TopicSharedAccessKeysInner object if successful.