#![allow(dead_code, deprecated, unused_variables, unused_mut)]
#![allow(dead_code)]
use std::cell::OnceCell;
struct Graph {
    edges: Vec<(i32, i32)>,
    span_tree_cache: OnceCell<Vec<(i32, i32)>>,
}
impl Graph {
    fn minimum_spanning_tree(&self) -> Vec<(i32, i32)> {
        self.span_tree_cache.get_or_init(|| self.calc_span_tree()).clone()
    }
    fn calc_span_tree(&self) -> Vec<(i32, i32)> {
        vec![]
    }
}
fn main() {}