proposition: Lemma ideal_subset_antisymm (I J : Ideal R) : I ⊆ J -> J ⊆ I -> I ↔ J.
proof: Proof. intros p q x; split; by revert x. Defined.
imports: Basics Types Spaces.Finite.Fin Classes.interfaces.abstract_algebra Algebra.Rings.CRing Algebra.AbGroups