get _inputNode() {
    if (this._ariaVersion === '1.1' && this._comboboxNode) {
      return /** @type {HTMLInputElement} */ (
        this._comboboxNode.querySelector('input') || this._comboboxNode
      );
    }
    return /** @type {HTMLInputElement} */ (this._comboboxNode);
  }
@configure FormControlMixin
Will tell FormControlMixin that a11y wrt labels / descriptions / feedback
should be applied here.
@protected