Bolt\Storage\EntityManager::createQueryBuilder PHP Method

    public function createQueryBuilder()
    {
        return new QueryBuilder($this->conn);
    }

 /**
  * @inheritdoc
  */
 public function persist(QuerySet $queries, $entity, EntityManager $em = null)
 {
     $field = $this->mapping['fieldname'];
     $target = $this->mapping['target'];
     $accessor = "get" . $field;
     $taxonomy = (array) $entity->{$accessor}();
     // Fetch existing relations
     $existingQuery = $em->createQueryBuilder()->select('*')->from($target)->where('content_id = ?')->andWhere('contenttype = ?')->andWhere('taxonomytype = ?')->setParameter(0, $entity->id)->setParameter(1, $entity->getContenttype())->setParameter(2, $field);
     $result = $existingQuery->execute()->fetchAll();
     $existing = array_map(function ($el) {
         return $el['slug'];
     }, $result);
     $proposed = $taxonomy;
     $toInsert = array_diff($proposed, $existing);
     $toDelete = array_diff($existing, $proposed);
     foreach ($toInsert as $item) {
         $ins = $em->createQueryBuilder()->insert($target);
         $ins->values(['content_id' => '?', 'contenttype' => '?', 'taxonomytype' => '?', 'slug' => '?', 'name' => '?'])->setParameters([0 => $entity->id, 1 => $entity->getContenttype(), 2 => $field, 3 => $item, 4 => $this->mapping['data']['options'][$item]]);
         $queries->append($ins);
     }
     foreach ($toDelete as $item) {
         $del = $em->createQueryBuilder()->delete($target);
         $del->where('content_id=?')->andWhere('contenttype=?')->andWhere('taxonomytype=?')->andWhere('slug=?')->setParameters([0 => $entity->id, 1 => $entity->getContenttype(), 2 => $field, 3 => $item]);
         $queries->append($del);
     }
 }