How to draw a trapezoid shape line in flutter using Rrect or similar?

I want to draw a trapezoidal shape in flutter, like this:

Now I am drawing an elliptical shape using Rrect for the same,

here is my code for drawing the second picture(getting an elliptical shape)

 @override
  void paint(Canvas canvas, Offset offset, ImageConfiguration cfg) {
    final Offset circleOffset =
        offset + Offset(cfg.size!.width / 2, cfg.size!.height + 8);
    canvas.drawRRect(
        RRect.fromRectAndRadius(
          Rect.fromCenter(center: circleOffset, width: 50, height: 5),
          Radius.circular(radius),
        ),
        _paint);
  }

using Rrect.fromRectAndCorners,

  {
    Radius topLeft = Radius.circular(10),
    ///top left corner curve or radius, in my case it is 10
    Radius topRight = Radius.circular(10),
    ///top right corner curve or radius, in my case it is 10
    Radius bottomRight = Radius.zero,
    ///bottom left corner curve or radius, in my case it is zero
    Radius bottomLeft = Radius.zero
    ///bottom right corner curve or radius, in my case it is zero
  }

so my final code looks like

@override
  void paint(Canvas canvas, Offset offset, ImageConfiguration cfg) {
    final Offset circleOffset =
        offset + Offset(cfg.size!.width / 2, cfg.size!.height + 8);
    canvas.drawRRect(
      RRect.fromRectAndCorners(
        Rect.fromCenter(center: circleOffset, width: 50, height: 5),
        bottomLeft: Radius.zero,
        bottomRight: Radius.zero,
        topLeft: Radius.circular(radius),
        topRight: Radius.circular(radius),
      ),
      _paint,
    );
  }

will get more details in the documentation here

https://api.flutter.dev/flutter/dart-ui/RRect/RRect.fromRectAndCorners.html

Thanks for help.