private async checkGRPC(rt: PermissionRelationTuple): Promise<CheckResponse> {
  const checkClient = this.checkClient;
  // Map the callback to a promise
  return new Promise<CheckResponse>(
    (resolve, reject) => checkClient.check(rt.toCheckRequest(),
      (error: ServiceError, response: CheckResponse) => {
        if (error) {
          return reject(error);
        }
        resolve(response);
      })
  );
}

{
  namespace: 'users',
  object: 'userId',
  relation: 'read_profile'
  subject_id: 'userId'
}