Doctrine\ODM\MongoDB\DocumentRepository::getDocumentManager PHP Method

    public function getDocumentManager()
    {
        return $this->dm;
    }

 /**
  * @param string $field
  * @return string
  */
 private function getField($field)
 {
     if ($this->fields === null) {
         $dm = $this->repository->getDocumentManager();
         /** @todo Investigate if produces performance problems */
         $entityMeta = $dm->getClassMetadata($this->repository->getDocumentName());
         foreach ($entityMeta->fieldMappings as $fieldName => $fieldMapping) {
             $this->fields[$fieldMapping['name']] = $fieldName;
         }
     }
     return isset($this->fields[$field]) ? $this->fields[$field] : $field;
 }