public function getCMSFields()
{
$fields = parent::getCMSFields();
/*
* MAIN TAB
*/
$tab = 'Root.Main';
//provides listbox field menu for selecting a predefined Icon
$data = DataObject::get('Icon');
$field = new ListboxField('MyIconID', 'My Icon');
$field->setSource($data->map('ID', 'Name')->toArray());
$field->setEmptyString('Select one');
$fields->addFieldToTab($tab, $field);
return $fields;
}