HarmonyOS怎么获取系统相册的路径

import photoAccessHelper from '@ohos.file.photoAccessHelper'; 
const context = getContext(this); 
let helper = photoAccessHelper.getPhotoAccessHelper(context); 
let uri = await helper.createAsset(photoAccessHelper.PhotoType.IMAGE, 'jpg'); 
let file = await fs.open(uri, fs.OpenMode.READ_WRITE | fs.OpenMode.CREATE); 
try { 
  context.resourceManager.getMediaContent($r('app.media.startIcon').id, 0) 
    .then(async value => { 
      let media = value.buffer; 
      // 写到媒体库文件中 
      await fs.write(file.fd, media); 
      await fs.close(file.fd); 
      AlertDialog.show({message:'已保存至相册!'}); 
    }); 
} 
catch (err) { 
  console.error("error is "+ JSON.stringify(err)) 
}