```rust use orgize::{Org, ast::Clock}; let clock = Org::parse("CLOCK: [2003-09-16 Tue 09:39]").first_node:: ().unwrap(); assert!(clock.duration().is_none()); let clock = Org::parse("CLOCK: [2003-09-16 Tue 09:39] =>12:00").first_node:: ().unwrap(); assert_eq!(clock.duration().unwrap(), "12:00"); ```
(&self)