protected function fetchPropertyValues($payload)
    {
        $propertyMap = $this->getPropertiesMap();
        $data = [];
        foreach ($payload['data'] as $resource) {
            $resource = (object)$resource;
            $resource = new \core_kernel_classes_Resource($resource->subject);
            $resourceData = $resource->getPropertiesValues($propertyMap);
            $entityInfo = array_map(function($row) use($resourceData) {
                $stringData = array_map(function($value){
                    return ($value instanceof \core_kernel_classes_Resource) ? $value->getUri() : (string) $value;
                }, $resourceData[$row]);
                return join(',', $stringData);
            }, $propertyMap);

            $entityInfo['uri'] = $resource->getUri();
            $entityInfo['id'] = \tao_helpers_Uri::encode($resource->getUri());
            $data[] = $entityInfo;
        }
        $payload['data'] = $data;

        return $payload;
    }