Function footprint_studies 

pub fn footprint_studies(
    flow: &Footprint,
    config: &FootprintStudyConfig,
) -> Vec<FootprintStudy>

Finds stacked imbalances, unfinished highs and lows, naked POCs, delta POCs, clusters, single prints and bars whose delta percentage or bid/ask ratio reaches a threshold, in the bars from Footprint::complete_from on.

Missing price rows break a stack. Stacks, POCs and unfinished levels end at the first subsequent bar whose executed range revisits them, or expire as config.extend_bars says; their state tells which. Call after trades change, not every paint: extending old zones scans subsequent bars.