proposition: Lemma adjoin_seqSr U rs1 rs2 : {subset rs1 <= rs2} -> (<<U & rs1>> <= <<U & rs2>>)%VS.
proof: Proof. by move/sub_span=> s_rs12; rewrite agenvS ?addvS. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq path) mathcomp(choice fintype div tuple finfun bigop ssralg) mathcomp(finalg zmodp matrix vector poly)