def on_service_departure(self, svc_ref):
        """
        Called when a service has been unregistered from the framework

        :param svc_ref: A service reference
        """
        with self._lock:
            if svc_ref is self.reference:
                # Forget about the service
                self._value.unset_service()

                # Clear the reference
                self.reference = None

                # Look for a replacement
                self._pending_ref = self._context.get_service_reference(
                    self.requirement.specification, self.requirement.filter
                )

                if self._pending_ref is None:
                    # No replacement found yet, wait a little
                    self.__still_valid = True
                    self.__timer_args = (self._value, svc_ref)
                    self.__timer = threading.Timer(
                        self.__timeout, self.__unbind_call, (False,)
                    )
                    self.__timer.start()

                else:
                    # Notify iPOPO immediately
                    self._ipopo_instance.unbind(self, self._value, svc_ref)
                return True

            return None
Called when a service has been unregistered from the framework

        :param svc_ref: A service reference