class ImageStyles

class ImageStyles extends DrupalSqlBase {
    
    /**
     * {@inheritdoc}
     */
    public function query() {
        return $this->select('image_styles', 'ims')
            ->fields('ims');
    }
    
    /**
     * {@inheritdoc}
     */
    public function fields() {
        $fields = [
            'isid' => $this->t('The primary identifier for an image style.'),
            'name' => $this->t('The style machine name.'),
            'label' => $this->t('The style administrative name.'),
        ];
        return $fields;
    }
    
    /**
     * {@inheritdoc}
     */
    public function getIds() {
        $ids['isid']['type'] = 'integer';
        return $ids;
    }
    
    /**
     * {@inheritdoc}
     */
    public function prepareRow(Row $row) {
        $effects = [];
        $results = $this->select('image_effects', 'ie')
            ->fields('ie')
            ->condition('isid', $row->getSourceProperty('isid'))
            ->execute();
        foreach ($results as $key => $result) {
            $result['data'] = unserialize($result['data']);
            $effects[$key] = $result;
        }
        $row->setSourceProperty('effects', $effects);
        return parent::prepareRow($row);
    }

}