method subscribe: client_id -> tutor_id list -> unit
method getUrl: client_id -> string
method getSubscription: client_id -> tutor_id list
method subscribe: client_id -> tutor_id list -> unit
method getUrl: client_id -> string
method getSubscription: client_id -> tutor_id list
method getHintType: tutor_id -> hint_type
method getDescription: tutor_id -> string
method index: tutor_dsc list
method getHintType: tutor_id -> hint_type
method getDescription: tutor_id -> string
method index: tutor_dsc list
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