demo of objectName() not working with QML (for me?)

qml_objectName_test.py

import sys
from PyQt5 import QtCore, QtQml, QtWidgets

QML = b'''
import QtQuick 2.7
import QtQuick.Window 2.2
import QtQuick.Controls 1.4
import ObjectNameTester 1.0

Window {
    visible: true
    ObjectNameTester {
        id: ont
        objectName: "myONT"
    }
    Button {
        text: "Do test"
        onClicked: ont.interact()
    }
}
'''

class ObjectNameTester(QtCore.QObject):
    @QtCore.pyqtSlot()
    def interact(self):
        name = self.objectName() # expecting 'myONT' here, but it gets ''
        print("objectName() is %r" % name)

if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv + ["-nograb"])
    QtQml.qmlRegisterType(ObjectNameTester, "ObjectNameTester", 1, 0, "ObjectNameTester")
    engine = QtQml.QQmlApplicationEngine()
    engine.loadData(QML)
    sys.exit(app.exec_())