protected function _getFieldToIdMapping(array $keys)
    {
        return $this->_table
            ->find('list', [
                'keyField' => $this->config('fields.key'),
                'valueField' => 'id'
            ])
            ->where([
                'scope' => $this->config('scope'),
                $this->config('fields.key') . ' IN' => $keys
            ])
            ->toArray();
    }