human
Solve the following python programming problem given the following code:
@ classmethod 
@ gen.coroutine 
def NotifyMergeViewpoint(cls, client, viewpoint_id, existing_followers, target_follower, source_user_id, act_dict, timestamp) : 
    'Notifies the target user that he has been added to the specified viewpoint. Invalidates
    the entire viewpoint so that the target user will load it in its entirety. Also notifies
    all specified existing followers of the viewpoint that a new follower has been added.
    Creates a merge activity in the viewpoint.
    ' 
    activity_func = NotificationManager._CreateActivityFunc (act_dict, Activity.CreateMergeAccounts, target_follower.user_id, source_user_id) 
    def _GetInvalidate(follower_id) : 
        if (follower_id == target_follower.user_id) : 
            return { 
                'viewpoints' : [NotificationManager._CreateViewpointInvalidation (viewpoint_id)], 
} 
else : 
            return { 
                'viewpoints' : [{ 
                    'viewpoint_id' : viewpoint_id, 
                    'get_followers' : True, 
}], 
} 
(yield NotificationManager._NotifyFollowers (client, viewpoint_id, (existing_followers + [timestamp]), _GetInvalidate, activity_func)) 

    
    

    Fix the buggy line: (yield NotificationManager._NotifyFollowers (client, viewpoint_id, (existing_followers + [timestamp]), _GetInvalidate, activity_func))
assistant
#Here is Python code to fix the buggy line: (yield NotificationManager.

(yield NotificationManager._NotifyFollowers (client, viewpoint_id, (existing_followers + [target_follower]), _GetInvalidate, activity_func))