pub trait Runnable:
Send
+ Sync
+ 'static {
// Required methods
fn step(&mut self, gc: &mut GC<OnionObjectCell>) -> StepResult;
fn format_context(&self) -> String;
// Provided method
fn receive(
&mut self,
step_result: &StepResult,
gc: &mut GC<OnionObjectCell>,
) -> Result<(), RuntimeError> { ... }
}