code: public Transaction beginTransaction() {
  		if (datastoreType == DatastoreType.HIGH_REPLICATION) {
  			return datastore.beginTransaction(TransactionOptions.Builder.withXG(true));
  		}
  		
  		return datastore.beginTransaction();
  	}
docs: Begins transaction and returns it.
  If the current application is using High Replication Datastore, this
  method returns XG (Cross-Group) transaction.
  
  @return Current transaction.