adsk-forge-LevelSectionPanel-step9

load() {
    if ( this.viewer.toolbar ) {
        // Toolbar is already available, create the UI
        this.createUI();
    } else {
       // Toolbar hasn't been created yet,
       //wait until we get notification of its creation
       this.viewer.addEventListener(
          Autodesk.Viewing.TOOLBAR_CREATED_EVENT,
          this.onToolbarCreated
        );
    }

    return true;
}