pub fn append(&mut self, other: &mut Self)
    where
        T: Ord,
    {
        self.map.append(&mut other.map);
    }
Gets an iterator that visits the values in the `BTreeSet` in ascending order.

# Examples

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

let set: BTreeSet<usize>
benchmarks/haystacks/code/rust-library.rs