In Twing, the object returned by `create_attribute()` doesn't have working methods

[MichaelAllenWarner]

Judging by this test.failing(), I figure this is a known problem, but I didn't see an issue for it: the object returned by a create_attribute() call doesn't have working methods.

I do have an example of a DrupalAttribute class with methods that work in Twing (it just adds a compatibility layer between Twing and the drupal-attribute npm package): https://github.com/MichaelAllenWarner/dte-storybook/blob/drupal-attribute/DrupalAttribute/index.js