You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: dancing_strings.rs
    path of file: ./repos/egui/crates/egui_demo_lib/src/demo
    
    the code of the file until where you have to start completion: use egui::{containers::*, *};

#[derive(Default)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[cfg_a
    
    fn ui(&mut self, ui: &mut Ui) {
        let color = if ui.visuals().dark_mode {
            Color32::from_additive_luminance(196)
        } else {
            Color32::from_black_alpha(240)
        };

        Frame::canvas(ui.style()).show(ui, |ui| {
            ui.ctx().request_repaint();
            let time = ui.input(|i| i.time);

            let desired_size = ui.available_width() * vec2(1.0, 0.35);
            let (_id, rect) = ui.allocate_space(desired_size);

            let to_screen =
                emath::RectTransform::from_to(Rect::from_x_y_ranges(0.0..=1.0, -1.0..=1.0), rect);

            let mut shapes = vec![];

            for &mode in &[2, 3, 5] {
                let mode = mode as f64;
                let n = 120;
                let speed = 1.5;

                let points: Vec<Pos2> = (0..=n)
                    .map(|i| {
                        let t = i as f64 / (n as f64);
                        let amp = (time * speed * mode).sin() / mode;
                        let y = amp * (t * std::f64::consts::TAU / 2.0 * mode).sin();
                        to_screen * pos2(t as f32, y as f32)
                    })
                    .collect();

                let thickness = 10.0 / mode as f32;
                shapes.push(epaint::Shape::line(points, Stroke::new(thickness, color)));
            }

            ui.painter().extend(shapes);
        });
        ui.vertical_centered(|ui| {
            ui.add(crate::egui_github_link_file!());
        });
    }