def METHOD_NAME(self, key, property_name):
    if key != self._key:
        return
    if property_name not in self._watched_properties:
        return
    value = self._getPropertyValue(property_name)
    if self._property_values.get(property_name, None) != value:
        self._property_values[property_name] = value
        self.propertiesChanged.emit()