protected function defaults($options, $relatedModel)
    {
        $defaults = [
            'model' => $relatedModel,
            'columnToSum' => 'total',
            'field' => $this->field($this->model, 'total'),
            'foreignKey' => $this->field($relatedModel, 'id'),
            'key' => 'id'
        ];

        return array_merge($defaults, $options);
    }