pub trait PoolManager {
// Required methods
fn extend(&mut self, more: usize);
fn shrink(&mut self, less: usize);
fn resize(&mut self, total: usize);
fn auto_adjust(&mut self);
fn auto_expire(&mut self, life: Option<Duration>);
fn kill_worker(&mut self, id: usize);
fn clear(&mut self);
fn close(&mut self);
fn force_close(&mut self);
}