code: public static final UUID encode(final TxnId txnId) {
          Preconditions.checkNotNull(txnId, "txnId");
          return new UUID(txnId.getHighBits(), txnId.getLowBits());
      }
docs: Returns UUID of transaction with given TxnId.
  
  @param txnId The Transaction Id.
  @return UUID of the transaction.