public ImmutableMap <TKey, TValue> SetItems([NotNull] IEnumerable <KeyValuePair <TKey, TValue> > items)
{
if (items is null)
{
throw new ArgumentNullException(nameof(items));
}
items = items.Materialize();
return(new ImmutableMap <TKey, TValue>(Base.SetItems(items), Reversed.SetItems(items.ReversePairs())));
}