def removeService(service):
        """
        Remove a child service.

        Only implementations of L{IService.disownServiceParent} should
        use this method.

        @type service: L{IService}
        @raise ValueError: Raised if the given service is not a child.
        @rtype: L{Deferred<defer.Deferred>}
        @return: a L{Deferred<defer.Deferred>} which is triggered when the
            service has finished shutting down. If shutting down is immediate,
            a value can be returned (usually, L{None}).
        """

        Remove a child service.

        Only implementations of L{IService.disownServiceParent} should
        use this method.

        @type service: L{IService}
        @raise ValueError: Raised if the given service is not a child.
        @rtype: L{Deferred<defer.Deferred>}
        @return: a L{Deferred<defer.Deferred>} which is triggered when the
            service has finished shutting down. If shutting down is immediate,
            a value can be returned (usually, L{None}).
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/application/service.py