No API requests are made by this method. If you want to create a new
topic, use {@see \Google\Cloud\PubSub\Topic::createTopic()}.
Example:
No API request yet!
$topic = $pubsub->topic('my-new-topic');
This will execute an API call.
echo $topic->info()['name']; // projects/my-awesome-project/topics/my-new-topic