/**
  * Renders a list box.
  * The selection of the list box is taken from the value of the model attribute.
  * @param array $items the option data items. The array keys are option values, and the array values
  * are the corresponding option labels. The array can also be nested (i.e. some array values are arrays too).
  * For each sub-array, an option group will be generated whose label is the key associated with the sub-array.
  * If you have a list of data models, you may convert them into the format described above using
  * [[\yii\helpers\ArrayHelper::map()]].
  *
  * Note, the values and labels will be automatically HTML-encoded by this method, and the blank spaces in
  * the labels will also be HTML-encoded.
  * @param array $options the tag options in terms of name-value pairs.
  *
  * For the list of available options please refer to the `$options` parameter of [[\yii\helpers\Html::activeListBox()]].
  *
  * If you set a custom `id` for the input element, you may need to adjust the [[$selectors]] accordingly.
  *
  * @return $this the field object itself
  */
 public function listBox($items, $options = [])
 {
     $options = array_merge($this->inputOptions, $options);
     $this->adjustLabelFor($options);
     $this->parts['{input}'] = Html::activeListBox($this->model, $this->attribute, $items, $options);
     return $this;
 }