proposition: Lemma prelift_perm_eq s1 s2 : perm_eq s1 s2 -> prelift s1 = prelift s2.
proof: Proof. exact: perm_big. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)