Doctrine\ODM\MongoDB\DocumentManager::createQueryBuilder PHP Method

    public function createQueryBuilder($documentName = null)
    {
        return new Query\Builder($this, $documentName);
    }

 /**
  * mongo_exists:users,email_address,10
  *
  * @param $attribute
  * @param $value
  * @param $parameters
  * @return bool
  */
 public function validate($attribute, $value, $parameters)
 {
     $collection = $parameters[0];
     if (empty($parameters[1])) {
         $field = 'id';
     } else {
         $field = $parameters[1];
     }
     return (bool) $this->documentManager->createQueryBuilder($collection)->field($field)->equals($value)->count()->getQuery()->execute();
 }