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: factory_async.rs
    path of file: ./repos/Relm4/examples
    
    the code of the file until where you have to start completion: use std::time::Duration;

use gtk::prelude::{BoxExt, ButtonExt, GtkWindowExt, OrientableExt, WidgetExt};
use relm4::factory::{
    AsyncFactoryComponent, AsyncFactorySender, AsyncFactoryVecDeque, DynamicIndex,
};
use relm4::loading_widgets::LoadingWidgets;
use relm4::{gtk, view, ComponentParts, ComponentSender, RelmApp, RelmWidgetExt, SimpleComponent};

#[derive(Debug)]
struct Counter {
    value: u8,
}

#[derive(Debug)]
enum CounterMsg {
    Increment,
    Decrement,
}

#[derive(Debug)]
enum CounterOutput {
    SendFront(DynamicIndex),
    MoveUp(DynamicIndex),
    MoveDown(DynamicIndex),
    Remove(DynamicIndex),
}

#[relm4::factory(async)]
impl AsyncFactoryComponent for Counter {
    type Init = u8;
    type Input = CounterMsg;
    type Output = CounterOutput;
    type CommandOutput = ();
    type ParentWidget = gtk::Box;

    view! {
        root = gtk::Box {
            #[name(label)]
            gtk::Label {
                #[watch]
                set_label: &self.value.to_string(),
                set_width_chars: 3,
            },

            #[name(add_button)]
            gtk::Button {
            
    
    fn update(&mut self, msg: Self::Input, _sender: ComponentSender<Self>) {
        let mut counters_guard = self.counters.guard();
        match msg {
            AppMsg::AddCounter => {
                counters_guard.push_back(self.created_widgets);
                self.created_widgets = self.created_widgets.wrapping_add(1);
            }
            AppMsg::RemoveCounter => {
                counters_guard.pop_back();
            }
            AppMsg::SendFront(index) => {
                counters_guard.move_front(index.current_index());
            }
            AppMsg::MoveDown(index) => {
                let index = index.current_index();
                let new_index = index + 1;
                // Already at the end?
                if new_index < counters_guard.len() {
                    counters_guard.move_to(index, new_index);
                }
            }
            AppMsg::MoveUp(index) => {
                let index = index.current_index();
                // Already at the start?
                if index != 0 {
                    counters_guard.move_to(index, index - 1);
                }
            }
            AppMsg::Remove(index) => {
                counters_guard.remove(index.current_index());
            }
        }
    }