bollinger

// Bollinger Bands (build_typed accepts variance=population|sample for the standard-deviation divisor; population is the default)
// Defaults of "bollinger" (see the indicator reference)
let params = HashMap::from([
    ("len".to_string(), 20.0),
    ("mult".to_string(), 2.0),
]);
let mut indicator = build_checked("bollinger", &params)?;

for bar in &bars {
    if let Some(output) = indicator.on_bar(bar) {
        // output.value, output.extra[...], indicator.alerts()
    }
}