method getByMusingId: musing_id -> client_id * tutor_id
method getByClientId: client_id -> musing_id list
method getByTutorId: tutor_id -> musing_id list
method getByMusingId: musing_id -> client_id * tutor_id
method getByClientId: client_id -> musing_id list
method getByTutorId: tutor_id -> musing_id list