function update($id, KalturaAnnotation $annotation)
 {
     $kparams = array();
     $this->client->addParam($kparams, "id", $id);
     $this->client->addParam($kparams, "annotation", $annotation->toParams());
     $this->client->queueServiceActionCall("annotation_annotation", "update", $kparams);
     if ($this->client->isMultiRequest()) {
         return $this->client->getMultiRequestResult();
     }
     $resultObject = $this->client->doQueue();
     $this->client->throwExceptionIfError($resultObject);
     $this->client->validateObjectType($resultObject, "KalturaAnnotation");
     return $resultObject;
 }