>>> (indent 4)
    children.add(new DrawerHeader(children: [
        new Flex([avatar, username],
            justifyContent: FlexJustifyContent.center,
            direction: FlexDirection.vertical)]));
<<<
    children.add(new DrawerHeader(children: [
      new Flex([avatar, username],
          justifyContent: FlexJustifyContent.center,
          direction: FlexDirection.vertical)
    ]));