#[local]
Hint Resolve union_ass : core.

(* Specifications: *)
Lemma seq_left : forall x y z:uniset, seq x y -> seq (union x z) (union y z).
#[local]
Hint Resolve seq_left : core.
Lemma seq_right : forall x y z:uniset, seq x y -> seq (union z x) (union z y).
#[local]
Hint Resolve seq_right : core.