used sum instead of fold.
@@ -2208,7 +2208,7 @@ pub trait Itertools: Iterator {
/// assert_eq!(
/// data.into_iter()
/// .into_group_map_by(|x| x.0)
- /// .map(|(key, values)| (key, values.into_iter().fold(0,|acc, (_,v)| acc + v )))
+ /// .map(|(key, values)| (key, values.into_iter().sum()))
/// .collect::<HashMap<u32,u32>>()[&0], 30)
/// ```
#[cfg(feature = "use_std")]
