Overrides \Drupal\views\Plugin\views\argument\ArgumentPluginBase::init().
Overrides ArgumentPluginBase::init
public function init(ViewExecutable $view, DisplayPluginBase $display, array &$options = NULL) {
parent::init($view, $display, $options);
$field = field_info_field($this->definition['field_name']);
$this->allowed_values = options_allowed_values($field);
}