How to launch/load local html for iOS?

I have a html file in assets/index.html, I can launch it for Android use the url like:

String localUrl = 'file:///android_asset/flutter_assets/assets/index.html';

What url should I use for iOS? Following is the launch code:

_flutterWebviewPlugin.launch(
    localUrl,
    ignoreSSLErrors: true,
    withLocalUrl: true,
    localUrlScope: 'assets/',
    allowFileURLs: true,
    hidden: true
);