1.

```rust
use std::fmt::Result;
use std::io::Result as IoResult;

fn main() {}
```

2.

```rust
use std::collections::*;

fn main() {
    let _c1:HashMap<&str, i32> = HashMap::new();
    let mut c2 = BTreeMap::new();
    c2.insert(1, "a");
    let _c3: HashSet<i32> = HashSet::new();
}
```

```rust
use std::collections::{HashMap, BTreeMap, HashSet};

fn main() {
    let _c1:HashMap<&str, i32> = HashMap::new();
    let mut c2 = BTreeMap::new();
    c2.insert(1, "a");
    let _c3: HashSet<i32> = HashSet::new();
}
```

3.

```rust
// in lib.rs

// Add this line
pub use crate::front_of_house::hosting;
```