pub trait Registry {
type NotifyListener;
// Required methods
fn register(&mut self, url: Url) -> Result<(), StdError>;
fn unregister(&mut self, url: Url) -> Result<(), StdError>;
fn subscribe(
&self,
url: Url,
listener: Self::NotifyListener
) -> Result<(), StdError>;
fn unsubscribe(
&self,
url: Url,
listener: Self::NotifyListener
) -> Result<(), StdError>;
}