code: public boolean txnRollbackPoll(long itemId, boolean backup) {
          TxQueueItem item = txMap.remove(itemId);
          if (item == null) {
              return false;
          }
  
          if (backup) {
              getBackupMap().put(itemId, item);
          } else {
              addTxItemOrdered(item);
          }
          cancelEvictionIfExists();
          return true;
      }
docs: Rolls back the effects of the {@link #txnPollReserve(long, String)}.
  The {@code backup} parameter defines whether this item was stored
  on a backup queue or a primary queue.
  It will return the item to the queue or backup map if it wasn't
  offered as a part of the transaction.
  Cancels the queue eviction if one is scheduled.
  
  @param itemId the ID of the item which was polled in a transaction
  @param backup if this is the primary or the backup replica for this queue
  @return if there was any polled item with the {@code itemId} inside a transaction