import sys

from PySide2.QtCore import Property, QObject, QUrl, Signal, Slot
from PySide2.QtGui import QGuiApplication
from PySide2.QtQml import QQmlApplicationEngine


class Backend(QObject):
    aNamedSignal = Signal(name='anotherNameForSignal')
    
    @Slot()
    def aSlotToCallSignal(self):
        self.aNamedSignal.emit()


if __name__ == '__main__':
    app = QGuiApplication(sys.argv)
    engine = QQmlApplicationEngine()

    backend = Backend()
    engine.rootContext().setContextProperty("backend", backend)

    engine.load(QUrl("main.qml"))

    if not engine.rootObjects():
        sys.exit(-1)

    sys.exit(app.exec_())