'Remove the activity and then fanout to user followers
:param user_id: the id of the user
:param activity: the activity which to remove'

def remove_user_activity(self, user_id, activity):

    user_feed = self.get_user_feed(user_id)
    user_feed.remove(activity)
    operation_kwargs = dict(activities=[activity], trim=False)
    for (priority_group, follower_ids) in self.get_user_follower_ids(user_id=user_id).items():
        for feed_class in self.feed_classes.values():
            self.create_fanout_tasks(follower_ids, feed_class, remove_operation, operation_kwargs=operation_kwargs, fanout_priority=priority_group)
    self.metrics.on_activity_removed()
