public function via($relationName, callable $callable = null)
    {
        $relation = $this->primaryModel->getRelation($relationName);
        $callableUsed = $callable !== null;
        $this->via = [$relationName, $relation, $callableUsed];
        if ($callable !== null) {
            call_user_func($callable, $relation);
        }

        return $this;
    }