proposition: Lemma inl_system_product_prop S S' (sd: inl_same_index S S'): inductive_system_on (inl_system_product sd) (inl_product_E S S') (isI S) (isr S) (inl_product_f S S').
proof: Proof. by []. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)