// lib.rs
#[derive(Default)]
struct Model {
    pub abc: i32,
}

enum Msg {
    ChangeA,
    ChangeB,
    ChangeC,
}
fn update(msg: Msg, model: &mut Model, orders: &mut impl Orders<Msg>) {
    match msg {
        Msg::ChangeA => model.abc = 1,
        Msg::ChangeB => model.abc = 2,
        Msg::ChangeC => model.abc = 3,

//ab.rs
guest_post(model.lang)