class ErrorResponsePart implements ResponsePartInterface
{
   /**
    * Error response part data.
    *
    * @var ResponseDtoInterface $partData
    */
   private $partData;

   /**
    * {@inheritdoc}
    */
   public function addData(ResponseDtoInterface $data) : void
   {
       if ($data instanceof ErrorDtoInterface) {
           $this->partData = $this->format($data);
       }
   }

   /**
    * Prepares response data.
    *
    * @param ResponseDtoInterface $data
    */
   public function format(ResponseDtoInterface $data) : void
   {
        if ($data instanceof ListDataDtoInterface) {
            $formatted = $data->getListData();
        } elseif (/* some expressions */) {
            // some logic
        } elseif (/* some expressions */) {
            // some logic
        }

       return $formatted ?? $data;
   }
}