private static IGrouping <TKey, TElement> Grouping <TKey, TElement>(TKey key, IEnumerable <TElement> elements) => HarshGrouping.Create(key, elements);
public IEnumerable <IGrouping <PropertyAccessor, TAttribute> > ReadableWritableInstancePropertiesWith <TAttribute>(Boolean inherit)
where TAttribute : Attribute
=> ReadableWritableInstanceProperties
.Select(p => HarshGrouping.Create(p, p.PropertyInfo.GetCustomAttributes <TAttribute>(inherit).ToArray()))
.Where(g => g.Any())
.ToArray();