docs: public HttpRequestFactory makeClient(DatastoreOptions options) {
      Credential credential = options.getCredential();
      HttpTransport transport = options.getTransport();
      if (transport == null) {
        transport = credential == null ? new NetHttpTransport() : credential.getTransport();
        transport = transport == null ? new NetHttpTransport() : transport;
      }
      return transport.createRequestFactory(credential);
    }