proposition: Lemma reverse_append {X} (x : X) (l : list X) : reverse (append x l) = x :: reverse l.
proof: Proof. unfold append. now rewrite reverse_concatenate, reverseStep, reverse_nil. Defined.
imports: UniMath.MoreFoundations.Tactics UniMath.Combinatorics.StandardFiniteSets UniMath.Combinatorics.Vectors