pub trait WeightScale<K, V> {
fn weight(&self, key: &K, value: &V) -> usize;
}
#[derive(Clone, Copy, Debug, Default)]
pub struct ZeroWeightScale;
impl<K, V> WeightScale<K, V> for ZeroWeightScale {
#[inline]
fn weight(&self, _: &K, _: &V) -> usize {
0
}
}