Function render_alert_levels 

pub fn render_alert_levels<'a>(
    ui: &mut Ui,
    mapping: &ChartMapping,
    alerts: impl IntoIterator<Item = &'a Alert>,
    color: Color32,
    labels: bool,
    active_only: bool,
    format: impl Fn(f64) -> String,
) -> Option<Alert>

Draw price thresholds and return a replacement alert after a drag. Supply only alerts for this pane, resolving symbol or watchlist membership in the host. With active_only unset, triggered, disabled and expired alerts are drawn dimmed. Call after drawing the chart, then submit the result through the host’s alerts service. Non-price sources require the host to resolve their own pane and coordinates. format supplies the instrument’s precision and currency for labels.