private @NotNull IntentionPreviewInfo doPreview(@NotNull Project project, PsiElement element, @Nullable Editor editor) {
    PsiFile file = element.getContainingFile();
    if (!(file instanceof XmlFile xmlFile)) return IntentionPreviewInfo.EMPTY;
    List<String> namespaces = getNamespaces(element, xmlFile);
    String namespace = namespaces.isEmpty() ? "" : namespaces.get(0);
    new MyStringToAttributeProcessor(element, project, editor, xmlFile)
      .doSomethingWithGivenStringToProduceXmlAttributeNowPlease(namespace);
    return IntentionPreviewInfo.DIFF;
  }
private @NotNull IntentionPreviewInfo doPreview(@NotNull Project project, PsiElement element, @Nullable Editor editor)