[PyQt] How to pass arguments in QDBusConnection connect() method

[Alfalfa]

I want to execute commands when some dbus signals are fired. Usually, I make a slot for each signals and it work just fine. However, in this case I need to attach signals dynamically, so a single slot must receive an argument in order to handle multiple signals. I was not able to use lambda like I would do for widgets signals. I tried combinations of all the commented approach below, and altough the connect method return True, the message is not delivered to the slot.

#!/usr/bin/python3
import sys
from PyQt5 import QtCore, QtWidgets, QtDBus

SIGNALS = \
{
    "0":
    {
        "description": "Mute speaker on resume",
        "bus": "system", ## todo
        "service": "org.freedesktop.login1",
        "path": "/org/freedesktop/login1",
        "interface": "org.freedesktop.login1.Manager",
        "name": "PrepareForSleep",
        "exec": "amixer -D pulse sset Master mute"
    }
}


class Main(QtCore.QObject):
    def __init__(self, parent):
        super().__init__()
        self.bus = QtDBus.QDBusConnection.systemBus()
        for num in SIGNALS:
            service = SIGNALS[num]["service"]
            path = SIGNALS[num]["path"]
            interface = SIGNALS[num]["interface"]
            name = SIGNALS[num]["name"]
            cmd = SIGNALS[num]["exec"]
            if QtDBus.QDBusConnection.systemBus().interface().isServiceRegistered(service).value():
                # connect(service, path, interface, name, signature, slot)
                #self.bus.connect(service, path, interface, name, "s", self._slot)

                # connect(service, path, interface, name, argumentMatch, signature, slot)
                self.bus.connect(service, path, interface, name, [cmd], "s", self._slot)
                #self.bus.connect(service, path, interface, name, [cmd], "o", self._slot)

    #@QtCore.pyqtSlot()
    #@QtCore.pyqtSlot(object)
    #@QtCore.pyqtSlot(list)
    @QtCore.pyqtSlot(str)
    def _slot(self, cmd):
        print(f"got '{cmd}'")

if __name__== '__main__':
    app = QtWidgets.QApplication(sys.argv)
    daemon = Main(app)
    sys.exit(app.exec_())