pub fn replace(&mut self, value: T) -> Option<T>
    where
        T: Ord,
    {
        Recover::replace(&mut self.map, value)
    }
Moves all elements from `other` into `Self`, leaving `other` empty.

# Examples

```
use std::collections::BTreeSet;

let mut a = BTreeSet::new();
a.insert(1);
a.insert(2);
a.insert(3);

let mut b = BTreeSet::new();
b.insert(3);
b.insert(4);
b.insert(5);

a.append(&mut b);

assert_eq!(a.len()
benchmarks/haystacks/code/rust-library.rs