proposition: Lemma sumv_pi_sum (I : finType) (P : pred I) Vs v (V : {vspace vT}) (defV : V = (\sum_(i | P i) Vs i)%VS) : v \in V -> \sum_(i | P i) sumv_pi_for defV i v = v :> vT.
proof: Proof. by apply: sumv_pi_uniq_sum; have [e _ []] := big_enumP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)