How to use the @microsoft/mixed-reality-extension-sdk.AssetContainer function in @microsoft/mixed-reality-extension-sdk

constructor(private _context: MRE.Context, private params: MRE.ParameterSet, private baseUrl: string) {
		this.assets = new MRE.AssetContainer(_context);

		this.context.onStarted(() => {
			this.setupShared();
			if (this.params.test === undefined) {
				this.menu.show();
			} else {
				this.activeTestName = this.params.test as string;
				this.activeTestFactory = Factories[this.activeTestName];
				this.setupRunner();
			}
		});
		this.context.onUserJoined((user) => this.userJoined(user));
		this.context.onUserLeft((user) => this.userLeft(user));
		this.backgroundMaterial = this.assets.createMaterial('background', {
			color: BackgroundColor
		});

constructor(private context: Context, private baseUrl: string) {
		this.assets = new AssetContainer(this.context);
		this.context.onStarted(this.started);
		this.context.onUserJoined(this.userJoined);
	}