Spec.G{ t_0 |-> { t_d |-> L } }
{ t_d |-> L } is the descendant lockset valid for the V value, because t_d was created in t_0 with the lockset being a superset of L.
type key = TID.ttype value = D.tval cardinal : t -> intval empty : unit -> tval is_empty : t -> boolval hash : t -> intval show : t -> stringval pretty : unit -> t -> Printable.Pretty.docval printXml : 'a BatInnerIO.output -> t -> unitval to_yojson : t -> Yojson.Safe.tval tag : t -> intval arbitrary : unit -> t QCheck.arbitraryval bot : unit -> tval is_bot : t -> boolval top : unit -> tval is_top : t -> bool