Macro rpc_notification 

macro_rules! rpc_notification {
    ($method:expr, $params:expr) => { ... };
    ($method:expr) => { ... };
}

Create a JSON-RPC notification

Usage:

// Notification with method and params
rpc_notification!("log", {"level": "info", "message": "Hello"})

// Notification with method only
rpc_notification!("ping")