Function collect_events 

fn collect_events(
    value: &Value,
    artist: &str,
    source: &str,
    now: u64,
    depth: usize,
    output: &mut BTreeMap<String, DiscoveredEvent>,
    review: &mut Vec<ReviewCandidate>,
)

Traverses only bounded JSON-LD graphs; arbitrary nested documents are not crawled.