public async Task <IPostingWarningCollection> CalculateAsync(IPostingLineCollection postingLineCollection)
{
NullGuard.NotNull(postingLineCollection, nameof(postingLineCollection));
Task <IPostingWarningCollection>[] calculationTasks = postingLineCollection.Select(CalculateAsync).ToArray();
IPostingWarningCollection[] postingWarningCollections = await Task.WhenAll(calculationTasks);
return(BuildPostingWarningCollection(postingWarningCollections.SelectMany(postingWarningCollection => postingWarningCollection)));
}