pub trait Graph {
// Required methods
fn node_count(&self) -> usize;
fn neighbors(&self, node: usize) -> Vec<usize>;
// Provided method
fn out_degree(&self, node: usize) -> usize { ... }
}pub trait Graph {
// Required methods
fn node_count(&self) -> usize;
fn neighbors(&self, node: usize) -> Vec<usize>;
// Provided method
fn out_degree(&self, node: usize) -> usize { ... }
}