(<=> (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)))