Pimcore\Model\Object\ClassDefinition\Data::getVersionPreview PHP Method

    public function getVersionPreview($data, $object = null, $params = [])
    {
        return "no preview";
    }

 /**
  * @see Object\ClassDefinition\Data::getVersionPreview
  * @param Asset\Image $data
  * @return string
  */
 public function getVersionPreview($data)
 {
     if ($data && $data->getType() == "asset" && $data->getData() instanceof Asset) {
         return '<img src="/admin/asset/get-video-thumbnail/id/' . $data->getData()->getId() . '/width/100/height/100/aspectratio/true" />';
     }
     return parent::getVersionPreview($data);
 }