Macro nebtm 

macro_rules! nebtm {
    ($hk:expr => $hv:expr, $( $xk:expr => $xv:expr ),* $(,)?) => { ... };
    ($hk:expr => $hv:expr) => { ... };
}

Like the crate::nem! macro, but for Binary Tree Maps.

use nonempty_collections::nebtm;

let m = nebtm! {"elves" => 3000, "orcs" => 10000};
assert_eq!(2, m.len().get());