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: lib.rs
    path of file: ./repos/tikv/components/test_backup/src
    
    the code of the file until where you have to start completion: // Copyright 2020 TiKV Project Authors. Licensed under Apache-2.0.

use std::{
    cmp, fs,
    path::{Path, PathBuf},
    sync::*,
    thread,
    time::Duration,
};

use 
    
    pub fn raw_kv_checksum(&self, start: String, end: String, cf: CfName) -> (u64, u64, u64) {
        let start = start.into_bytes();
        let end = end.into_bytes();

        let mut total_kvs = 0;
        let mut total_bytes = 0;

        let sim = self.cluster.sim.rl();
        let mut engine = sim.storages[&self.context.get_peer().get_store_id()].clone();
        let snap_ctx = SnapContext {
            pb_ctx: &self.context,
            ..Default::default()
        };
        let snapshot = engine.snapshot(snap_ctx).unwrap();
        let mut iter_opt = IterOptions::default();
        if !end.is_empty() {
            iter_opt.set_upper_bound(&end, DATA_KEY_PREFIX_LEN);
        }
        let mut iter = snapshot.iter(cf, iter_opt).unwrap();

        if !iter.seek(&start).unwrap() {
            return (0, 0, 0);
        }
        let digest = crc64fast::Digest::new();
        let mut checksum: u64 = 0;
        while iter.valid().unwrap() {
            let key = iter.key();
            let value = iter.value();
            total_kvs += 1;
            total_bytes += (key.len() + value.len()) as u64;
            checksum = checksum_crc64_xor(checksum, digest.clone(), key, value);
            iter.next().unwrap();
        }
        (checksum, total_kvs, total_bytes)
    }