Section MapAxioms.
Variables A B C : Type.
Definition eqmap (m m':Map A) := eqm A (MapGet A m) (MapGet A m').

Lemma MapMerge_ext :
forall m1 m2 m'1 m'2:Map A,
eqmap m1 m'1 ->
eqmap m2 m'2 -> eqmap (MapMerge A m1 m2) (MapMerge A m'1 m'2).