code: def add_user_story_attribute(self, name, **attrs):
          
          return UserStoryAttributes(self.requester).create(
              self.id, name, **attrs
          )
docs: Add a new User Story attribute and return a
          :class:`UserStoryAttribute` object.
  
          :param name: name of the :class:`UserStoryAttribute`
          :param attrs: optional attributes for :class:`UserStoryAttribute`