Function `format`

fn format<'a, I, B>(w: &mut Formatter<'_>, date: Option<&NaiveDate>, time: Option<&NaiveTime>, off: Option<&(String, FixedOffset)>, items: I) -> Result
where
    I: Iterator<Item = B> + Clone,
    B: Borrow<Item<'a>>

Tries to format given arguments with given formatting items. Internally used by DelayedFormat.