Function update 

pub fn update(
    layout: &Layout,
    id: &str,
    new_state: Option<&str>,
    new_priority: Option<char>,
    block_add: Option<&str>,
    block_clear: Option<&str>,
) -> Result<UpdateOutcome>

Change state, priority, or blocker edges. Adding a blocker to an open issue moves it to BLOCKED; clearing the last blocker moves it back to TODO.