fact: Definition iota_fun (R:A->B-> Prop) : A -> B := fun a => iota Hb (fun b':B => In DA a /\ R a b' /\ In DB b').
imports: Coq(ClassicalDescription Ensembles Image ProofIrrelevance) ZornsLemma(EnsemblesImplicit FunctionProperties ImageImplicit) hydras(MoreEpsilonIota)