 model
       * is either another templatize instance that had option `parentModel: true`,
       * or else the host element.
       *
       * @return {Polymer.PropertyEffectsInterface} The parent model of this instance
       */
      get parentModel() {
        let model = this.__parentModel;
        if (!model) {
          let options;
          model = this
          do {
            // A template instance's `__dataHost` is a <template>
            // `model.__dataHost.__dataHost` is the template's hos