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: db.rs
    path of file: ./repos/sled/src
    
    the code of the file until where you have to start completion: use std::ops::Deref;

use crate::*;

const DEFAULT_TREE_ID: &[u8] = b"__sled__default";

/// The `sled` embedded database! Implements
/// `Deref<Target = sled::Tree>` to refer to
/// a default keyspace / namespace / 
    
    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
    /// let old = old_sled::open("my_old__db")?;
    ///
    /// // may be a different version of sled,
    /// // the export type is version agnostic.
    /// let new = sled::open("my_new__db")?;
    ///
    /// let export = old.export();
    /// new.import(export);
    ///
    /// assert_eq!(old.checksum()?, new.checksum()?);
    /// # drop(old);
    /// # drop(new);
    /// # std::fs::remove_file("my_old__db");
    /// # std::fs::remove_file("my_new__db");
    /// # Ok(()) }