      */
        _getLabel(item) {
          return this.labelPath ? item[this.labelPath] : item;
        }

        /**
         * Fills the list of checked options.
         */
        _updateValue() {
          this.value = [...this.shadowRoot.querySelectorAll('vaadin-checkbox')]
            .filter(cb => cb.checked)
            .map(cb => cb.dataset.value);
        }
      }

      customElements.define(OptionGroupElement.is, OptionGroupElement);

      /**
       * @namespace ExpenseManager
       */
 