code: def add_user_story(self, subject, **attrs):
          
          return UserStories(self.requester).create(
              self.id, subject, **attrs
          )
docs: Adds a :class:`UserStory` and returns a :class:`UserStory` resource.
  
          :param subject: subject of the :class:`UserStory`
          :param attrs: other :class:`UserStory` attributes