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: crates_cache.rs
    path of file: ./repos/cargo-supply-chain/src
    
    the code of the file until where you have to start completion: use crate::api_client::RateLimitedClient;
use crate::publishers::{PublisherData, PublisherKind};
use flate2::read::GzDecoder;
use serde::{Deserialize, Serialize};
use std::{
    collections::{BTreeSet, HashMap},
    fs,
    io::{self, ErrorKind},
    path::PathBuf,
    time::Duration,
    time::SystemTimeError,
};

pub struct CratesCache {
    cache_dir: Option<CacheDir>,
    metadata: Option<MetadataStored>,
    
    
    fn commit(&mut self) -> io::Result<()> {
        let mut uncommitted_files = std::mem::take(&mut self.staged_files);
        let metadata_file = uncommitted_files.take(CratesCache::METADATA_FS);
        for file in uncommitted_files {
            let source = self.dir.join(&file).with_extension("part");
            let destination = self.dir.join(&file);
            fs::rename(source, destination)?;
        }
        // metadata_file is special since it contains the timestamp for the cache.
        // We will only commit it and update the timestamp if updating everything else succeeds.
        // Otherwise it would be possible to create a partially updated cache that's considered fresh.
        if let Some(file) = metadata_file {
            let source = self.dir.join(&file).with_extension("part");
            let destination = self.dir.join(&file);
            fs::rename(source, destination)?;
        }
        Ok(())
    }