proposition: Lemma fgraph_ffun0 aT0 : fgraph (ffun0 aT0) = nil :> seq rT.
proof: Proof. by apply/nilP/eqP; rewrite size_tuple. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype tuple)