private static async Task <IGrouping <TKey, TElement> > AwaitGrouping <TKey, TElement>(
IAsyncGrouping <TKey, TElement> asyncGrouping)
{
if (asyncGrouping is null)
{
throw new ArgumentNullException(nameof(asyncGrouping));
}
var key = asyncGrouping.Key;
var enumerable = await asyncGrouping.ConfigureAwait(false);
return(new Grouping <TKey, TElement>(key, enumerable));
}
