For a collection of pairs, group by the first item in the pair.
For a collection of pairs, group by the first item in the pair.
a builder to construct collections of items that have been grouped
Map from first items of the pairs to collections of items that have been grouped
For a collection of pairs, group by the first item in the pair.
For a collection of pairs, group by the first item in the pair.
Map from first items of the pairs to collections of items that have been grouped