public void LoadFromXml (XmlReader reader)
		{
			reader.ReadToDescendant ("plist");
			while (reader.Read () && reader.NodeType != XmlNodeType.Element);
			if (!reader.EOF)
				root = LoadFromNode (reader);
		}
		public PlistDocument (PlistObjectBase root)
		{
			this.root = root;
		}
		static void SetIfNotPresent (PlistDictionary dict, string key, PlistObjectBase value)
		{
			if (!dict.ContainsKey (key))
				dict[key] = value;
		}