pub fn pop_last(&mut self) -> Option<T>
    where
        T: Ord,
    {
        self.map.pop_last().map(|kv| kv.0)
    }
Removes and returns the value in the set, if any, that is equal to the given one.

The value may be any borrowed form of the set's value type,
but the ordering on the borrowed form *must* match the
ordering on the value type.

# Examples

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

let mut set: BTreeSet<_> = [1, 2, 3].iter(
benchmarks/haystacks/code/rust-library.rs