protected function getRelationInputs($inputs = [])
    {
        $relations = [];

        foreach ($inputs as $column => $value) {
            if (method_exists($this->model, $column)) {
                $relation = call_user_func([$this->model, $column]);

                if ($relation instanceof Relation) {
                    $relations[$column] = $value;
                }
            }
        }

        return $relations;
    }