code: public function createRouter($debug = false)
      {
          if (null === $this->routesFile) {
              throw new LogicException('The derived class must define the string variable "routesFile"');
          }
  
          if (!is_string($this->routesFile)) {
              throw new LogicException('"routesFile" variable must be a string value');
          }
  
          $isProduction = $this->configurationHandler->isProduction();
  
          $cacheDir = null;
          if (!$debug && $isProduction) {
              $cacheDir = $this->configurationHandler->siteCacheDir() . '/routes';
          }
  
          $this->router = new Router(
              new YamlFileLoader($this->fileLocator),
              $this->routesFile,
              array('cache_dir' => $cacheDir)
          );
  
          return $this->router;
      }
docs: Creates the router
  
  @param bool $debug
  
  @return null|\Symfony\Component\Routing\Router