public function toResource()
{
$protocol = $this->collection->database->connection->registerFileStreamWrapper();
$context = stream_context_create([$protocol => ['download' => $this]]);
$document = $this->getDocument();
$url = "{$protocol}://{$this->collection->database->name}.{$this->collection->prefix}?_id={$document['_id']}";
return fopen($url, 'r', false, $context);
}