You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: persister.rs
    path of file: ./repos/talent-plan/courses/dss/raft/src/raft
    
    the code of the file until where you have to start completion: //! Support for Raft and kvraft to save persistent
//! Raft state (log &c) and k/v server snapshots.
//!
//! we will use the original persister.rs to test your code for grading.
//! so, while you can modify this code to help you debug, please
//! test with the original before submitting.

use std::sync::{Arc, Mutex};

pub trait Persister: Send + 'static {
    fn raft_state(&self) -> Vec<u8>;
    fn save_raft_state(&self, state: Vec<u8>);
    fn save_state_and_snapshot(&self, state: Vec<u8>, snapshot: Vec<u8>);
    fn snapshot(&self) -> Vec<u8>;
}


    
    fn test_object_safety() {
        let sp = SimplePersister::new();
        sp.save_raft_state(vec![111]);
        let obj: Box<dyn Persister + Sync> = Box::new(sp);
        assert_eq!(obj.raft_state(), vec![111]);
        obj.save_state_and_snapshot(vec![222], vec![123]);
        assert_eq!(obj.raft_state(), vec![222]);
        assert_eq!(obj.snapshot(), vec![123]);

        let cloneable_obj: Arc<dyn Persister> = Arc::new(obj);
        assert_eq!(cloneable_obj.raft_state(), vec![222]);
        assert_eq!(cloneable_obj.snapshot(), vec![123]);

        let cloneable_obj_ = cloneable_obj.clone();
        cloneable_obj.save_raft_state(vec![233]);
        assert_eq!(cloneable_obj_.raft_state(), vec![233]);
        assert_eq!(cloneable_obj_.snapshot(), vec![123]);

        let sp = SimplePersister::new();
        let obj: Arc<dyn Persister + Sync> = Arc::new(sp);
        let _box_obj: Box<dyn Persister> = Box::new(obj);
    }