Does itertools::Combinations makes any guarantees about the order in which it yields combinations?

The docs provide this example:

use itertools::Itertools;

let it = (1..5).combinations(3);
itertools::assert_equal(it, vec![
    vec![1, 2, 3],
    vec![1, 2, 4],
    vec![1, 3, 4],
    vec![2, 3, 4],
]);

Which at a glance is constructing the combinations by "indexing" the iterator (1..5) with lexicographically sorted indices [0, 1, 2], [0, 1, 3], [0, 2, 3], and [1, 2, 3].

I am wondering if this is something I can rely on, or if it is an implementation detail that should not be relied on?