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

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