Function run 

pub fn run(
    name: &str,
    capabilities: Value,
    handler: impl FnMut(&str, Value) -> Result<Value, Refusal> + 'static,
) -> i32

The loop of a state machine, whatever the target: natively, crate::serve on the standard input and output until they end, its exit code answered; in a module, handler kept for the turns to come.