'user_id stops following target_user_id
:param user_id: the user which is doing the unfollowing
:param target_user_id: the user which is being unfollowed
:param async: controls if the operation should be done via celery'

def unfollow_user(self, user_id, target_user_id, async=True):

    self.unfollow_many_users(user_id, [target_user_id], async)
