code: public function getAliasIdForLanguage($language)
      {
          /** @var ReadSiteAliasInterface $alias */
          foreach ($this->aliases as $key => $alias) {
              if ($alias->getLanguage() == $language) {
                  return $key;
              }
          }
  
          return null;
      }
docs: Return alias id for given language
  
  @param string $language
  
  @return int