pyside2-uic general unicode string, which canot detect by both pyside2-lupdate and pylupdate5

1. create 'untitled.ui' by pyside2-designer.exe
2. pyside2-uic.exe untitled.ui -o ui_untitled.py. The code is unicode string like this:

MainWindow.setWindowTitle(QCoreApplication.translate("MainWindow", u"MainWindow", None))
self.pushButton.setText(QCoreApplication.translate("MainWindow", u"hello world. \u4e2d\u6587", None))

      3. pyside2-lupdate -noobsolete ui_untitled.py -ts i18n_pysid2-ludate.ts

          (or pylupdate5 -noobsolete ui_untitled.py -ts i18n_pylupdate5.ts)

      The result of pyside2-lupdate:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE TS><TS version="1.1">
</TS>

Maybe i think pyside2-uic.exe should genate UTF-8 Text instead unicode string，like pyuic5.exe: 

MainWindow.setWindowTitle(_translate("MainWindow", "MainWindow"))
self.pushButton.setText(_translate("MainWindow", "hello world. 中文"))