proposition: Lemma class_supportEr A B : class_support A B = \bigcup_(x in B) A :^ x.
proof: Proof. exact: curry_imset2r. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype div path tuple bigop prime finset)