docs: public void changeField( MappedAttributeDefinition defn,
                               ModelNode newValue ) throws RepositoryException, OperationFailedException {
          ModeShapeEngine engine = getEngine();
          String repositoryName = repositoryName();
  
          // Get a snapshot of the current configuration ...
          RepositoryConfiguration config = engine.getRepositoryConfiguration(repositoryName);
  
          // Now start to make changes ...
          Editor editor = config.edit();
  
          // Find the Document containing the field ...
          EditableDocument fieldContainer = editor;
          for (String fieldName : defn.getPathToContainerOfField()) {
              fieldContainer = editor.getOrCreateDocument(fieldName);
          }
  
          // Get the raw value from the model node ...
          Object rawValue = defn.getTypedValue(newValue);
  
          // Change the field ...
          String fieldName = defn.getFieldName();
          fieldContainer.set(fieldName, rawValue);
  
          // Apply the changes to the current configuration ...
          Changes changes = editor.getChanges();
          engine.update(repositoryName, changes);
      }