code: List<JcError> store(Map<Long, Integer> elementVersionsMap) {
  		List<JcError> ret = null;
  		ITransaction txToClose = null;
  		try {
  			if (isModified()) {
  				txToClose = this.resultHandler.createLockingTxIfNeeded();
  				ret = this.resultHandler.store(elementVersionsMap);
  			} else
  				ret = Collections.emptyList();
  		} finally {
  			if (txToClose != null) { // we have created the transaction
  				if (ret == null)
  					ret = new ArrayList<JcError>();
  				ret.addAll(txToClose.close());
  			}
  		}
  		return ret;
  	}
docs: Update the underlying database with changes made on the graph
  @return a list of errors, which is empty if no errors occurred