/**
* Applies callback to query for easier elaborate custom queries
* on find (actually: ->first()) calls.
*
* @param Closure $callback must return query/builder compatible
* @param array $columns
* @return Collection
* @throws InvalidArgumentException
*/
public function findCallback(Closure $callback, $columns = ['*'])
{
return $this->postProcess(parent::findCallback($callback, $columns));
}