code: public function createQueryBuilder($findDrafts = false)
      {
          /* @var \Doctrine\MongoDB\Query\Builder $qb */
          /** @noinspection PhpUndefinedClassInspection */
          /** @noinspection PhpUndefinedMethodInspection */
          $qb = parent::createQueryBuilder();
  
          if (null !== $findDrafts) {
              $qb->field('isDraft')->equals($findDrafts);
          }
          return $qb;
      }
docs: Creates a query builder.
  
  Prepopulate the constraint for 'isDraft' according to $findDrafts:
  - true: queryBuilder will return only drafts
  - false: queryBuilder will return only non drafts.
  - null: queryBuilder will return all entities matching the additional constraints.
  
  @param bool|null $findDrafts
  
  @return \Doctrine\MongoDB\Query\Builder