Inheritance: ConditionTreeItem
		private void OnAddGroup(ConditionGroup group)
		{
			ConditionGroup newGroup = new ConditionGroup();
			group.Items.Add(newGroup);
			newGroup.Parent = group;
		}
		private void OnAddEpression(ConditionGroup group)
		{
			PropertyExpression propertyExpression = new PropertyExpression();
			propertyExpression.Property = InstanceProperties.Properties.FirstOrDefault();
			group.Items.Add(propertyExpression);
			propertyExpression.Parent = group;
		}
		protected override ConditionTreeItem CopyPlainItem()
		{
			ConditionGroup copiedGroup = new ConditionGroup();
			copiedGroup.Type = Type;
			return copiedGroup;
		}