How can I remove this gray line from ExpansionTile? (Flutter)

Question

How can I remove this gray line from ExpansionTile in flutter?

The Code

ExpansionTile(
          title: Text(
            "Title",
            style: TextStyle(
              fontSize: 18.0,
              fontWeight: FontWeight.bold
            ),
          ),
          children: <Widget>[
            ListTile(
              title: Text(
                'data'
              ),
            )
          ],
        ),

Answer 1

You can solve this applying a transparent color to the dividerColor in the ThemeData in your MaterialApp definition.

MaterialApp(
   title: 'Your Flutter App',
   theme: ThemeData(
      primarySwatch: Colors.blue,
      dividerColor: Colors.transparent,
  ),

Of course you can make your own implementation of a custom widget.