public Task<IReadOnlyList<EntityVersion<WebResourceName, string>>> GetTodoVersions (DateTimeRange? range)
{
if (range != null)
throw new NotSupportedException ("range not supported");
return Task.FromResult<IReadOnlyList<EntityVersion<WebResourceName, string>>> (
_entites.Select (e => EntityVersion.Create (e.Key, e.Value.Item1)).ToList());
}