* @param progressMonitor the progress monitor, can be {@code null}
*/
public void mergeFrom(final DataSet from, ProgressMonitor progressMonitor) {
final DataSetMerger visitor = new DataSetMerger(data,from);
try {
visitor.merge(progressMonitor);
} catch (DataIntegrityProblemException e) {
JOptionPane.showMessageDialog(
Main.parent,
e.getHtmlMessage() != null ? e.getHtmlMessage() : e.getMessage(),
tr("Error"),