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;
 }
 public Student(int id, string name, Group group)
 {
     this.id = id;
     this.name = name;
     this.group = group;
 }
 partial void DeleteGroup(Group instance);
 partial void UpdateGroup(Group instance);
 partial void InsertGroup(Group instance);