Function set_startup_banner 

pub fn set_startup_banner<F>(f: F)
where
    F: Fn() + Send + Sync + 'static,

Registers a startup banner callback that will be invoked once, the first time ModCli::run() is called in this process. If the environment variable MODCLI_DISABLE_BANNER is set to “1” or “true” (case-insensitive), the banner will be suppressed.

Note: This can only be set once per process.