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;
 }