Macro kv_pairs

macro_rules! kv_pairs {
    ($($k:expr_2021 => $v:expr_2021),* $(,)?) => { ... };
}

Construct the key value attribute slice using mapping syntax. Example:

assert_eq!(
    kv_pairs!("1" => "1", "2" => 2, "3" => 3.0),
    &[
        key_value!("1", "1"),
        key_value!("2", 2),
        key_value!("3", 3.0),
    ],
);