partial void DeleteLesson(Lesson instance);
 partial void UpdateLesson(Lesson instance);
		private void detach_Lessons(Lesson entity)
		{
			this.SendPropertyChanging();
			entity.Part = null;
		}
 partial void InsertLesson(Lesson instance);
		private void attach_Lessons(Lesson entity)
		{
			this.SendPropertyChanging();
			entity.Part = this;
		}