code: def service(self, name: str = None):
          
          if self._services_initialized:
              from warnings import warn
              warn('Services have already been initialized. Please register '
                   f'{name} sooner.')
              return lambda x: x
  
          def wrapper(service):
              self.register_service(name, service)
              return service
          return wrapper
docs: Decorator to mark something as a service.