code: public function getDrupalSelector($name)
      {
          $selectors = $this->getDrupalParameter('selectors');
  
          if (!isset($selectors[$name])) {
              throw new \Exception(sprintf('No such selector configured: %s', $name));
          }
  
          return $selectors[$name];
      }
docs: Get selector by name.
  
  @param string $name
  Selector name from the configuration file.
  
  @return string
  CSS selector.
  
  @throws \Exception
  If selector does not exits.