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: ops.rs
    path of file: ./repos/wasmer/lib/virtual-fs/src
    
    the code of the file until where you have to start completion: //! Common [`FileSystem`] operations.
#![allow(dead_code)] // Most of these helpers are used during testing

use std::{
    collections::VecDeque,
    path::{Path, PathBuf},
};

use futures::future::BoxFuture;
use tokio::io::{AsyncReadExt, AsyncWriteExt};

use crate:
    
    async fn create_dir_all() {
        let fs = MemFS::default();
        super::write(&fs, "/file.txt", b"").await.unwrap();

        assert!(!super::exists(&fs, "/really/nested/directory"));
        super::create_dir_all(&fs, "/really/nested/directory").unwrap();
        assert!(super::exists(&fs, "/really/nested/directory"));

        // It's okay to create the same directory multiple times
        super::create_dir_all(&fs, "/really/nested/directory").unwrap();

        // You can't create a directory on top of a file
        assert_eq!(
            super::create_dir_all(&fs, "/file.txt").unwrap_err(),
            FsError::BaseNotDirectory
        );
        assert_eq!(
            super::create_dir_all(&fs, "/file.txt/invalid/path").unwrap_err(),
            FsError::BaseNotDirectory
        );
    }