old_contents: import {PolymerElement} from '@polymer/polymer/polymer-element.js';
  import {SirenEntityMixin} from './siren-entity-mixin.js';
  import {html} from '@polymer/polymer/lib/utils/html-tag.js';
  import './notes/note.js';
  
  class MyVirtualNotebook extends SirenEntityMixin(PolymerElement) {
  
  	static get template() {
  		return html`
  <h1>My Virtual Notebook</h1>
  <template is="dom-repeat" items="[[notes]]">
  	<d2l-note href="{{item}}" token="{{token}}"></d2l-note>
  </template>
  `;
  	}
  
  	static get properties() {
  		return {
  			notes: {
  				type: Array,
  				value: []
  			}
  		};
  	}
  
  	static get observers() {
  		return [
  			'_changed(entity)'
  		];
  	}
  
  	static get is() {
  		return 'my-virtual-notebook';
  	}
  
  	_changed() {
  		this._getUrlForNotes(this.href);
  	}
  
  	async _getUrlForNotes(href) {
  		const response = await fetch(href)
  			.then(res => res.json());
  		this.notes = response.entities.map(e => e.href);
  	}
  }
  
  window.customElements.define(MyVirtualNotebook.is, MyVirtualNotebook);
  
new_contents: import {PolymerElement} from '@polymer/polymer/polymer-element.js';
  import {SirenEntityMixin} from './siren-entity-mixin.js';
  import {html} from '@polymer/polymer/lib/utils/html-tag.js';
  import './notes/note.js';
  
  class MyVirtualNotebook extends SirenEntityMixin(PolymerElement) {
  
  	static get template() {
  		return html`
  <h1>My Virtual Notebook</h1>
  <template is="dom-repeat" items="[[notes]]">
  	<d2l-note href="{{item}}" token="{{token}}"></d2l-note>
  </template>
  `;
  	}
  
  	static get properties() {
  		return {
  			notes: {
  				type: Array,
  				value: []
  			}
  		};
  	}
  
  	static get observers() {
  		return [
  			'_changed(entity)'
  		];
  	}
  
  	static get is() {
  		return 'my-virtual-notebook';
  	}
  
  	_changed(entity) {
  		if( entity && entity.entities ) {
  			this.notes = entity.entities.map(subEntity => subEntity.href);
  		}
  	}
  }
  
  window.customElements.define(MyVirtualNotebook.is, MyVirtualNotebook);
  
subject: Use entity from SirenEntityMixin instead of fetch/parsing itself