code: public Observable<List<EventSubscriptionInner>> listRegionalByResourceGroupForTopicTypeAsync(String resourceGroupName, String location, String topicTypeName) {
          return listRegionalByResourceGroupForTopicTypeWithServiceResponseAsync(resourceGroupName, location, topicTypeName).map(new Func1<ServiceResponse<List<EventSubscriptionInner>>, List<EventSubscriptionInner>>() {
              @Override
              public List<EventSubscriptionInner> call(ServiceResponse<List<EventSubscriptionInner>> response) {
                  return response.body();
              }
          });
      }
docs: List all regional event subscriptions under an Azure subscription and resource group for a topic type.
  List all event subscriptions from the given location under a specific Azure subscription and resource group and topic type.
  
  @param resourceGroupName The name of the resource group within the user's subscription.
  @param location Name of the location
  @param topicTypeName Name of the topic type
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the List&lt;EventSubscriptionInner&gt; object