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 DeleteTeacher(Teacher instance);
 partial void UpdateTeacher(Teacher instance);
 partial void InsertTeacher(Teacher instance);