@Override
  public Collection<PsiElement> getAdditionalElementsToDelete(@NotNull final PsiElement element,
                                                              final @NotNull Collection<? extends PsiElement> allElementsToDelete,
                                                              final boolean askUser) {
    if (!askUser || !(element instanceof PsiFile)) return Collections.emptyList();

    final VirtualFile file = ((PsiFile)element).getVirtualFile();
    if (file == null) return Collections.emptyList();

    final Collection<NestingTreeStructureProvider.ChildFileInfo> relatedFileInfos =
      NestingTreeStructureProvider.getFilesShownAsChildrenInProjectView(element.getProject(), file);

    final Collection<PsiElement> psiFiles = new ArrayList<>(relatedFileInfos.size());
    for (NestingTreeStructureProvider.ChildFileInfo info : relatedFileInfos) {
      final PsiFile psiFile = element.getManager().findFile(info.file());
      if (psiFile != null && !allElementsToDelete.contains(psiFile)) {
        psiFiles.add(psiFile);
      }
    }

    if (!psiFiles.isEmpty()) {
      final String message = psiFiles.size() == 1
                             ? RefactoringBundle.message("ask.to.delete.related.file", ((PsiFile)psiFiles.iterator().next()).getName())
                             : RefactoringBundle.message("ask.to.delete.related.files",
                                                         StringUtil.join(psiFiles, (psiFile) -> ((PsiFile)psiFile).getName(), ", "));
      final int ok =
        Messages.showYesNoDialog(element.getProject(), message, RefactoringBundle.message("delete.title"), Messages.getQuestionIcon());
      if (ok == Messages.YES) {
        return psiFiles;
      }
    }

    return Collections.emptyList();
  }
@Override
  public Collection<PsiElement> getAdditionalElementsToDelete(@NotNull final PsiElement element,
                                                              final @NotNull Collection<? extends PsiElement> allElementsToDelete,
                                                              final boolean askUser)