intros.
simpl.
unfold monoid_expec.
unfold expec, compose.
simpl.
rewrite (monoidHomo_zero mh)...
Qed.

(* Specifications: *)
Lemma monoid_expec_bind_leaf_plus (X Y: Set) (f: X -> MonoidMonadTrans.M m ne_tree_monad.ext Y)
(n: prod m X):
monoid_expec (@bind (MonoidMonadTrans.M m ne_tree_monad.ext) _ _ (ne_tree.Leaf n) f) =
INR (ms (fst n)) + monoid_expec (f (snd n)).