code: function isSpecs(opt) {
      //logger.debug('???');
      //logger.debug(`${opt.cacheDir}`);
      //let b:any = opt.cacheDir instanceof(String)
      if (!path.isAbsolute(opt.cacheDir)) {
          logger.error('cacheDir parameter must be an absolute path');
          return false;
      }
      if ('cacheDir' in opt && 'tcp' in opt && 'port' in opt && 'engineSpec' in opt)
          return typeof (opt.cacheDir) == 'string' && typeof (opt.tcp) == 'string' &&
              typeof (opt.port) == 'number' && engineLib.isEngineSpec(opt.engineSpec);
      //logger.debug('niet');
      return false;
  }
docs: VR change typeguard to warehouse