get state of executed system.

It is possible to get the state of an executed system back out?
Something like this?
```rust
#[system]
fn example(#[state] s: &mut u32) {}

fn test(){
let sys = example_system(0);
let mut schedule = Schedule::builder()
.add_system(&mut sys)
.build();
schedule.execute(world, resources);
let s = sys.states().s();
}
```

Specifics can change, it is about the general concept.