code: public TransactionWriteRequest addUpdate(Object object, DynamoDBTransactionWriteExpression transactionWriteExpression) {
          return addUpdate(object, transactionWriteExpression, null /* returnValuesOnConditionCheckFailure */);
      }
docs: Adds update operation (to be executed on object) to the list of transaction write operations.
  transactionWriteExpression is used to conditionally update object.