Macro s 

macro_rules! s {
    ( $( $axis:expr ),* $(,)? ) => { ... };
}

Build a SliceSpec from axis expressions.

use rlx_tensor::{ax, graph, rg, s, shape};

let g = graph("win", |g| {
    let x = g.input("x", shape![4, 16]);
    x.slice(s![ax(), rg(2, 10)])
});
assert_eq!(g.outputs.len(), 1);