Correct the following snippet

     draw_contours(
            &mut output_image,
            &contours,
            -1, // Draw all contours
            Scalar::new(0.0, 255.0, 0.0, 0.0), // Green color
            3,                                 // Thickness
            imgproc::LINE_8,
            &mut hierarchy,
            255,
            Point::new(0, 0),
        ).unwrap();