code: public ListClustersResponse getClusters() {
      logger.info("Reading clusters.");
      return client.listCluster(
        ListClustersRequest.newBuilder().setParent(instanceName.getInstanceName()).build());
    }
docs: Gets a {@link ListClustersResponse} that contains all of the clusters for the
  projectId/instanceId configuration.
  @return all clusters in the instance if the instance ID is provided; otherwise, all clusters in
  project are returned.