Macro tr 

macro_rules! tr {
    ($key:expr_2021 $(,)?) => { ... };
    ($key:expr_2021, $($arg:expr_2021),+ $(,)?) => { ... };
}

tr!("key") = tr("key"); tr!("key", a, b) fills the text’s %s specifiers with a and b (anything Display) — see format_translation.