protected function exposedRelationsFromRequest($model = null)
    {
        $exposedRelations = static::$exposedRelations;

        // if no relations are to be included by request
        if (count($this->request->include) == 0) {
            // and if we have a model
            if ($model !== null && $model instanceof Model) {
                // then use the relations exposed by default
                $exposedRelations = array_intersect($exposedRelations, $model->defaultExposedRelations());
                $model->setExposedRelations($exposedRelations);
                return $exposedRelations;
            }

        }

        $exposedRelations = array_intersect($exposedRelations, $this->request->include);
        if ($model !== null && $model instanceof Model) {
            $model->setExposedRelations($exposedRelations);
        }

        return $exposedRelations;
    }