code: public function addSecondaryDnsDomains($domain2add, $ip){
          self::getClient()->addSecondaryDnsDomains($this->getDomain(),$domain2add,$ip);
          return true;
      }
docs: Add domain to secondary DNS
  
  @param string $domain2add
  @param string ipv4 $ip
  @return bool true
  @throws Exception\ServerException
  @throws \Ovh\Common\Exception\BadMethodCallException