code: function alreadyRegistered (paramName) {
      let params = router.params;
      if (!params && router._router) {
        params = router._router.params;
      }
  
      return params && params[paramName] &&
        (params[paramName].indexOf(pathParamMiddleware) >= 0);
    }
docs: Determines whether we've already registered path-param middleware for the given parameter.
  
  @param   {string}    paramName
  @returns {boolean}