public function getSearchable()
    {
        // When there is no node type we exclude source attributes
        if (is_null($this->getNodeTypeName()))
        {
            return $this->searchable;
        }

        $modelName = source_model_name($this->getNodeTypeName(), true);

        return array_merge_recursive(
            $this->searchable,
            call_user_func([$modelName, 'getSearchable'])
        );
    }