proposition: Lemma mapi_in_iff {elt elt'} m x (f:key->elt->elt') : In x (mapi f m) <-> In x m.
proof: Proof. rewrite !in_find. destruct (mapi_find f m x) as (y,(_,->)). apply option_map_some. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)