public static void IndexerSet <TBase>(ITypeSet <TBase> instance, Type key, TBase value)
 {
     IDictionaryContracts.IndexerSet(instance, key);
     Contracts.Requires.That(value.GetType().IsImplementationOfType(key));
 }
 public static void IndexerGet <TBase>(ITypeSet <TBase> instance, Type key) =>
 IDictionaryContracts.IndexerGet(instance, key);