/**
  * Helper function for #isMetaInfoInFolderHierarchyUnique to recurse into
  * child folders and check for unique meta info.
  *
  * @param \Conjoon\Data\Entity\Mail\MailFolderEntity $folder
  * @param $metaInfo string
  *
  * @return boolean
  *
  * @throws FolderServiceException
  * @throws FolderDoesNotExistException
  */
 protected function checkMetaInfoType(\Conjoon\Data\Entity\Mail\MailFolderEntity $folder, $metaInfo)
 {
     if ($folder->getMetaInfo() !== $metaInfo) {
         return false;
     }
     $childFolders = $this->getChildFolderEntities($folder);
     foreach ($childFolders as $childFolder) {
         if ($this->checkMetaInfoType($childFolder, $metaInfo) !== true) {
             return false;
         }
     }
     return true;
 }