HarmonyOS api10如何给子窗口设置圆角

sub_windowClass.setUIContent("pages/subWindowPage", (err: BusinessError) => {  
  let errCode: number = err.code;  
  if (errCode) {  
    console.error('Failed to load the content. Cause:' + JSON.stringify(err));  
    return;  
  }  
  //子窗口加载页面成功后，可以设置窗口背景色，全透明  
  (sub_windowClass as window.Window).setWindowBackgroundColor('#00000000')