public Timetable(int id, DateTime dateTimeStart, Group group, Subject subject, Teacher teacher)
 {
     this.id = id;
     this.group = group;
     this.subject = subject;
     this.teacher = teacher;
     this.dateTimeStart = dateTimeStart;
 }
 partial void DeleteSubject(Subject instance);
 partial void UpdateSubject(Subject instance);
 partial void InsertSubject(Subject instance);