code: private function getAccSys($assetTypeCode)
      {
          $req = new \Praxigento\Accounting\Api\Service\Account\Get\Request();
          $req->setIsSystem(TRUE);
          $req->setAssetTypeCode($assetTypeCode);
          $resp = $this->servAccount->exec($req);
          $result = $resp->getId();
          return $result;
      }
docs: Get system account ID by asset type ID.
  
  @param string $assetTypeCode
  @return int