function getCheckedOutDocs($repositoryId, $folderId = null, $filter = '', $includeAllowableActions, $includeRelationships, $maxItems = 0, $skipCount = 0)
 {
     $checkedout = array();
     $results = $this->ktapi->get_checkedout_docs(false);
     foreach ($results as $document) {
         $CMISDocument = new CMISDocumentObject($document->getId(), $this->ktapi);
         // set version label property - possibly belongs in document class
         $CMISDocument->setProperty('VersionLabel', $CMISDocument->getProperty('VersionSeriesCheckedOutId'));
         $checkedout[] = $CMISDocument->getProperties();
     }
     return $checkedout;
 }