static public T Convert <KEY_TYPE, VALUE_TYPE, T>(this LookupBackedSet <KEY_TYPE, VALUE_TYPE> item, KEY_TYPE key, Operation <T> default_operation, Operation <T, VALUE_TYPE> operation)
{
if (item.IsAsBacked(key))
{
return(default_operation.Execute());
}
return(operation.Execute(item.Lookup(key)));
}