[LayaAir 2.0]2.0版本，Particle2D is not a constructor

export default class RunMain extends Laya.Sprite{

    constructor(){

        super();

        Laya.loader.load([{url:"res/213.part",type:Laya.Loader.JSON}],Laya.Handler.create(this,this.onAssetsLoaded));

    }

    onAssetsLoaded(){

       let pg = Laya.loader.getRes("res/213.part");

       let pd = new Laya.Particle2D(pg);

    }

}