code: public ResourceListKeysInner listKeys(String resourceGroupName, String namespaceName, String notificationHubName, String authorizationRuleName) {
          return listKeysWithServiceResponseAsync(resourceGroupName, namespaceName, notificationHubName, authorizationRuleName).toBlocking().single().body();
      }
docs: Gets the Primary and Secondary ConnectionStrings to the NotificationHub.
  
  @param resourceGroupName The name of the resource group.
  @param namespaceName The namespace name.
  @param notificationHubName The notification hub name.
  @param authorizationRuleName The connection string of the NotificationHub for the specified authorizationRule.
  @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 ResourceListKeysInner object if successful.