@Nullable
  @Override
  protected RefactoringEventData getBeforeData() {
    RefactoringEventData data = new RefactoringEventData();
    final List<PsiElement> fields = new ArrayList<>();
    for (FieldDescriptor fieldDescriptor : myFieldDescriptors) {
      fields.add(fieldDescriptor.getField());
    }
    data.addElements(fields);
    return data;
  }
@Nullable
  @Override
  protected RefactoringEventData getBeforeData()