Function update_pred 

pub fn update_pred(
    layout: &Layout,
    id: &str,
    new_state: Option<&str>,
    new_priority: Option<char>,
    block_add: Option<&str>,
    block_clear: Option<&str>,
    pred: UpdatePred<'_>,
) -> Result<UpdateOutcome>

update with a last-seen predicate.

Errors

Same as update, plus Error::StaleWrite when the predicate fails.