code: def on_service_arrival(self, svc_ref):
          
          with self._lock:
              if self.reference is None:
                  # Inject the service
                  service = self._context.get_service(svc_ref)
                  self.reference = svc_ref
                  self._value.set_service(service)
                  self.__still_valid = True
  
                  # Cancel timer
                  self.__cancel_timer()
  
                  # Bind the service
                  self._ipopo_instance.bind(self, self._value, self.reference)
                  return True
  
              return None
docs: Called when a service has been registered in the framework
  
          :param svc_ref: A service reference