文件管理包含什么功能，要如何使用

import UIAbility from '@ohos.app.ability.UIAbility';
import window from '@ohos.window';

export default class EntryAbility extends UIAbility {
 onWindowStageCreate(windowStage: window.WindowStage) {
   let context = this.context;
   let pathDir = context.filesDir;
 }
}