Axiom HleafNodeConst: forall x p leafIdx lvl dt,
              isLeafNode x (writeToNode p leafIdx lvl dt) ->
              isLeafNode x p.

Lemma init_invariantholds: forall (memSz : nat) (op : Op) (bID : nat) (dataN : option nat) (s0 : st_rand), init_invariant s0 memSz -> let (_, s) := runState (access op bID dataN) s0 in init_invariant s memSz.