Yog Script (.ys, .yns) analyzed: its lexer, parser and syntax tree, names resolved, the class index model — what the build and the editors read a source with.
namespace System.Linq;
/// The items of one key (`GroupBy`), gone through as its items.
[Intrinsic]
public interface IGrouping<out TKey, out TElement> : IEnumerable<TElement> {
TKey Key { get; }
}