code: def register_signal_handler(self, signal_name, handler_function):
          
          self.bus.add_signal_receiver(signal_wrapper(handler_function),
                                       signal_name=signal_name,
                                       dbus_interface=self.IFACE,
                                       bus_name=self.name,
                                       path=self.OBJ_PATH)
docs: register `handler_function` to receive `signal_name`.
  
          Uses class's dbus interface self.IFACE, objects name self.name
          and objects path self.OBJ_PATH to match signal.
  
          :param str signal_name: The signal name;
                                  None(default) matches all names.
          :param function handler_function: The function to be called.