How to use an OptionsetField ?

<?php
class ArticleHolder extends Page {

private static $allowed_children = array('ArticlePage');
private static $db=array(
   'MyType' => "Varchar(10)"
);

public function getCMSFields() {
$fields = parent::getCMSFields();
   $typeField = new OptionsetField(
      $name = "MyTypeID",
      $title = "Type de conteneur",
      $source = array(
      "1" => "Option 1",
      "2" => "Option 2",
      "3" => "Option 3",
      "4" => "Option 4",
      "5" => "Option 5"
      )

      );
$fields->addFieldToTab('Root.Main',$typeField,'Content');
return $fields;
}

}
class ArticleHolder_Controller extends Page_Controller {
}