     }
      }
    },

    observers: [
      '_updateAttrForSelected(attrForSelected)',
      '_updateSelected(selected)',
      '_checkFallback(fallbackSelection)'
    ],

    created: function() {
      this._bindFilterItem = this._filterItem.bind(this);
      this._selection = new Polymer.IronSelection(this._applySelection.bind(this));
    },

    attached: function() {
      this._observer = this._observeItems(this);
      this._updateItems();
      if (!this._shouldUpdateSelection) {
        this._upd