proposition: Lemma msuppM_incl g1 g2 : msupp (g1 * g2) `<=` [fset (k1 * k2)%M | k1 in msupp g1, k2 in msupp g2].
proof: Proof. apply/fsubsetP => k /msuppM_le [k1 [k2 [k1g1 k2g2 ->]]]. by apply/imfset2P; exists k1; last exists k2. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq path choice finset fintype finfun) mathcomp(tuple bigop ssralg ssrint ssrnum) xfinmap