def exists(self, client=None):
        client = self._require_client(client)
        api = client.publisher_api

        try:
            api.topic_get(topic_path=self.full_name)
        except NotFound:
            return False
        else:
            return True
API call:  test for the existence of the topic via a GET request
dataset/ETHPy150Open GoogleCloudPlatform/gcloud-python/gcloud/pubsub/topic.py/Topic.exists