code: public CloseableResource<JobMasterClient> acquireMasterClientResource() {
      return new CloseableResource<JobMasterClient>(mJobMasterClientPool.acquire()) {
        @Override
        public void close() {
          mJobMasterClientPool.release(get());
        }
      };
    }
docs: Acquires a job master client from the job master client pool. The resource is
  {@code Closeable}.
  
  @return the acquired job master client resource