fs_student_mapper = mapper(
        FSStudent, 
        fs_student_table,
        properties={
                'person': relation(
                        FSPerson, 
                        #backref='br_students', 
                        primaryjoin = and_(fs_student_table.c.fodselsdato == fs_person_table.c.fodselsdato, fs_student_table.c.personnr == fs_person_table.c.personnr),
                        foreign_keys = [fs_student_table.c.fodselsdato, fs_student_table.c.personnr],
                        remote_side = [fs_person_table.c.fodselsdato, fs_person_table.c.personnr],
                )
        }
)