kes an [`Ordering`] argument which describes the memory ordering of this operation.
Possible values are [`SeqCst`], [`Acquire`] and [`Relaxed`].

# Panics

Panics if `order` is [`Release`] or [`AcqRel`].

# Examples

```
use portable_atomic::{AtomicU64, Ordering};

let some_var = AtomicU64::new(5);

assert_eq!(some_var.load(Ordering::Relaxed), 5);
```