Macro finish 

macro_rules! finish {
    () => { ... };
}

Finish a Canic canister module.

Place this macro at the end of the canister’s crate root after start!, start_local!, or start_wasm_store! and after any extra endpoint definitions. In debug builds it exports Candid for local .did generation; in non-debug builds it only satisfies the required Canic finish marker.