pub struct Formatter<L : Language = English>{...}

impl Formatter {
    pub fn new() -> Formatter<English>;
    pub fn with_language(l: Language) -> Self;
    pub fn num_items(&mut self, x: usize) -> &mut Self;
    pub fn max_unit(&mut self, x: TimeUnit) -> &mut Self;
    pub fn min_unit(&mut self, x: TimeUnit) -> &mut Self;
    pub fn too_low(&mut self, x: &'static str) -> &mut Self;
    pub fn too_high(&mut self, x: &'static str) -> &mut Self;
    pub fn max_duration(&mut self, x: Duration) -> &mut Self;
    pub fn ago(&mut self, x: &'static str) -> &mut Self;
    
    pub fn convert(&self, d: Duration) -> String;
    pub fn convert_chrono(&self, from: chrono::DateTime, to: chrono::DateTime) -> String;
}

pub fn from_isolang(x : isolang::Language) -> Option<Box<Language>>;

pub fn format_5chars(d: Duration) -> String;