code: def _start(self):
          
          try:
              # Try to register to factory events
              with use_ipopo(self.__context) as ipopo:
                  ipopo.add_listener(self)
          except BundleException:
              # Service not yet present
              pass
  
          # Register the iPOPO service listener
          self.__context.add_service_listener(self, specification=SERVICE_IPOPO)
docs: Starts the instantiation queue (called by its bundle activator)