(* Precondition for sewing in a qhmap is satified: *)

(* Specifications: *)
Lemma inv_qhmap_l_12:
forall (m:fmap)(k:dim)(x y:dart),
inv_qhmap m -> prec_lh m k x y ->
prec_Lq (B_1 (B m k x) k y) k x y.