pub trait Purchaseable {
// Required methods
fn get_purchase(&self, id: u64) -> Option<Purchase>;
fn get_purchase_mut(&mut self, id: u64) -> Option<&mut Purchase>;
}pub trait Purchaseable {
// Required methods
fn get_purchase(&self, id: u64) -> Option<Purchase>;
fn get_purchase_mut(&mut self, id: u64) -> Option<&mut Purchase>;
}