queueThangType (slug) {
    this.loadingThangTypes.set(
      slug,
      (async () => {
        const attr = await getThang({ slug })
        this.loadedThangTypes.set(slug, new ThangType(attr))
      })()
    )
  }
Queues a ThangType resource for async loading.
@param {string} slug ThangType slug.