Doctrine\ODM\MongoDB\PersistentCollection::getDeleteDiff PHP Method

    public function getDeleteDiff()
    {
        return array_udiff_assoc($this->snapshot, $this->coll->toArray(),
                function($a, $b) {return $a === $b ? 0 : 1;});
    }

 /**
  * {@inheritdoc}
  */
 public function getDeleteDiff()
 {
     return $this->collection->getDeleteDiff();
 }