Modified or before value in model

Have a look at this:

https://docs.phalcon.io/en/latest/reference/models.html#record-snapshots

I didn't see it before, but this is the functionnality i need.

In the documentation, i can't see how get before values, i can only check if the value has change. I find this in C files : getSnapshotData but it's missing in the documentation

And i have a bug, i use it like this

class Product extends Phalcon\Mvc\Model {
  public function initialize(){
    $this->keepSnapshots(true);
  }
  public function afterSave(){
    print_r($this->getChangedFields());
    exit();
  }
}

And i get many fields of other model, not only the product model.