rst call for that
       * template, and the cached class is returned for all subsequent calls to
       * `templatize` for that template.  As such, `options` callbacks should not
       * close over owner-specific properties since only the first `options` is
       * used; rather, callbacks are called bound to the `owner`, and so context
       * needed from the callbacks (such as references to `instances` stamped)
       * should be stored on the `owner` such that they can be retrieved via `this`.
       