fact: Definition prod_fst_rel {A B : Type} (R : relationH (A * B) (A * B)) : relationH A A := fun x y => forall (b1 b2 : B), R (x, b1) (y, b2).
imports: Coq(Morphisms Setoid Relation_Definitions RelationClasses ) ITree(Basics.Utils Indexed.Sum)