Collect Values form an Iterator into a BTreeSet in Rust

use std::collections::BTreeSet;

fn main() {
  let items = vec![
    "alfa", "bravo", "alfa", 
    "charlie", "alfa", "bravo"
  ];

  let refined = BTreeSet::from_iter(
    items.iter().map(|item| item.to_uppercase())
  );

  for item in refined {
    println!("{}", item);
  }

}