code: public TransactionConfigurationBuilder transactionManagerLookup(TransactionManagerLookup tml) {
        attributes.attribute(TRANSACTION_MANAGER_LOOKUP).set(tml);
        if (tml != null) {
           this.transactionMode(TransactionMode.TRANSACTIONAL);
        }
        return this;
     }
docs: Configure Transaction manager lookup directly using an instance of TransactionManagerLookup.
  Calling this method marks the cache as transactional.