public function convert(Query $query, \Core\Mapper\MapperInterface $mapper)
 {
     $mongoQuery = $this->convertCondition($query->getCondition());
     $cursor = $mapper->getCollection()->find($mongoQuery);
     $cursor->sort($this->convertSort($query->getSort()));
     $limit = $query->getLimit();
     if ($limit) {
         $cursor->limit($limit->count)->skip($limit->offset);
     }
     return $cursor;
 }