pub trait CostModel {
// Required method
fn cost(&self, enode: &IKun) -> Cost;
// Provided method
fn weights(&self) -> (f64, f64, f64) { ... }
}pub trait CostModel {
// Required method
fn cost(&self, enode: &IKun) -> Cost;
// Provided method
fn weights(&self) -> (f64, f64, f64) { ... }
}