public boolean checkCanModify(final Collection<? extends PackagingNodeSource> nodeSources) {
    if (nodeSources.isEmpty()) {
      return true;
    }

    if (nodeSources.size() > 1) {
      Messages.showErrorDialog(myArtifactsEditor.getMainComponent(),
                               JavaUiBundle.message(
                                 "error.message.the.selected.node.consist.of.several.elements.so.it.cannot.be.edited"));
    }
    else {
    final PackagingNodeSource source = ContainerUtil.getFirstItem(nodeSources, null);
      if (source != null) {
        Messages.showErrorDialog(myArtifactsEditor.getMainComponent(),
                                 JavaUiBundle.message(
                                   "error.message.the.selected.node.belongs.to.0.element.so.it.cannot.be.edited",
                                   source.getPresentableName()));
      }
    }
    return false;

  }
public boolean checkCanModify(final Collection<? extends PackagingNodeSource> nodeSources)