human
Solve the following python programming problem given the following code:
def addService(self, service, parentService = None) : 
    "
        Add a service. 
        
        The :func:`toil.job.Job.Service.start` method of the service will be called         after the run method has completed but before any successors are run.         The service's :func:`toil.job.Job.Service.stop` method will be called once         the successors of the job have been run. 
        
        Services allow things like databases and servers to be started and accessed         by jobs in a workflow.
        
        :raises toil.job.JobException: If service has already been made the child of a job or another service.
        :param toil.job.Job.Service service: Service to add.
        :param toil.job.Job.Service parentService: Service that will be started before 'service' is
               started. Allows trees of services to be established. parentService must be a service
               of this job.
        :return: a promise that will be replaced with the return value from
                 :func:`toil.job.Job.Service.start` of service in any successor of the job.
        :rtype:toil.job.PromisedJobReturnValue
        " 
    if (parentService is not None) : 
        def check(services) : 
            for (s, jS) in services : 
                if ((s == parentService) or check (s._childServices)) : 
                    return True 
return False 
if (not check (self._services)) : 
            raise JobException ('Parent service is not a service of the given job') 
return parentService._addChild (service) 
else : 
        if service._hasParent : 
            raise JobException ('The service already has a parent service') 
service._hasParent = True 
        jobService = ServiceJob (service) 
        self._services.append ((parentService, jobService)) 
        return jobService.rv () 

    
    

    Fix the buggy line: self._services.append ((parentService, jobService))
assistant
#Here is Python program to fix the buggy line: self.

self._services.append ((service, jobService))