(<=> (Set-Partition ?S @Sets) (And (= ?S (Union @Sets)) (Pairwise-Disjoint @Sets)))
(Undefined (Arity Set-Partition))
(Instance-Of (Arity Set-Partition) Undefined) (<=> (Set-Partition ?S @Sets) (And (= ?S (Union @Sets)) (Pairwise-Disjoint @Sets)))