proposition: Lemma limit_unique f x y: limit_of f x -> limit_of f y -> x = y.
proof: Proof. by move => [_ pa pb] [_ pc pd]; apply: (limit_unique2 pa pc pb pd). Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(fintype bigop)