code: public void close() {
      if (gcs != null) {
        logger.atFine().log("close()");
        try {
          gcs.close();
        } finally {
          gcs = null;
  
          if (updateTimestampsExecutor != null) {
            try {
              shutdownExecutor(updateTimestampsExecutor, /* waitSeconds= */ 10);
            } finally {
              updateTimestampsExecutor = null;
            }
          }
  
          if (cachedExecutor != null) {
            try {
              shutdownExecutor(cachedExecutor, /* waitSeconds= */ 5);
            } finally {
              cachedExecutor = null;
            }
          }
        }
      }
    }
docs: Releases resources used by this instance.