pub trait CacheKey {
// Required method
fn cache_key(&self, state: &mut dyn Hasher);
// Provided method
fn cache_key_hash(&self) -> u64 { ... }
}pub trait CacheKey {
// Required method
fn cache_key(&self, state: &mut dyn Hasher);
// Provided method
fn cache_key_hash(&self) -> u64 { ... }
}