pub trait Visitor {
// Provided methods
fn on_syntax_down(&mut self, node: &Node, ctl: &mut JourneyControls) { ... }
fn on_syntax_up(&mut self, node: &Node) { ... }
fn visit_class_or_object_key(&mut self, key: &ClassOrObjectMemberKey) { ... }
fn visit_class_or_object_value(&mut self, value: &ClassOrObjectMemberValue) { ... }
fn visit(&mut self, n: &Node) { ... }
}