/// <summary>
/// Wraps this <see cref="HoconValue"/> into a new <see cref="Config"/> object at the specified key.
/// </summary>
/// <param name="key">The key designated to be the new root element.</param>
/// <returns>A <see cref="Config"/> with the given key as the root element.</returns>
public Config AtKey(string key)
{
var o = new HoconObject();
o.GetOrCreateKey(key);
o.Items[key] = this;
var r = new HoconValue();
r.Values.Add(o);
return new Config(new HoconRoot(r));
}