proposition: Lemma mdomU i : finsupp U_(i)%M = [fset i].
proof: Proof. by apply/fsetP=> j; rewrite -!cmE_neq0 cmU in_fset1 eqb0 negbK. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap