_onBeforeRepropagateChildrenValues(ev) {
      // Normalize target, since we might receive 'portal events' (from children in a modal,
      // see select-rich)
      const target = (ev.detail && ev.detail.element) || ev.target;
      if (this.multipleChoice || !target.checked) {
        return;
      }
      this.formElements.forEach(option => {
        if (target.choiceValue !== option.choiceValue) {
          option.checked = false; // eslint-disable-line no-param-reassign
        }
      });
      this.__setChoiceGroupTouched();
      this.requestUpdate('modelValue', this._oldModelValue);
      this._oldModelValue = this.modelValue;
    }
@override FormControlMixin
@param {CustomEvent} ev
@protected