Polymorphic belongsTo?

I have an attachment table that contains records that could belong to a lot or a product.

Trying to get lot working first.

// attachment.js
export default Model.extend({
  title: attr(),
  owner: belongsTo('attachable', {polymorphic: true})
// attachable.js
export default Model.extend({
  'attachments': hasMany('attachment')
import attachable from '../lib/attachable'

// lot.js
export default attachable.extend({
  refNumber: attr('string')

I get an error thrown when running this.

No model was found for 'attachable'

What is the proper way to set-up such a relationship?

What location within the project are you storing these models? app/models/?

yes, in app/models