Definition inj_on_list {A B} (l : list A) (f : A -> B) :=
forall x y, In x l -> In y l -> f x = f y -> x = y.
Definition subset_rel {X} (sub lst : list X) : Prop :=
forall x,
In x sub ->
In x lst.
(*** NoDup general lemmas ***)

Lemma NoDup_get_write_back_blocks : forall `{C : Config} lst p lvl pos_map,
NoDup (List.map block_blockid lst) ->
NoDup (List.map block_blockid
(get_write_back_blocks p lst 4 lvl pos_map)).