Multiset
A carrier domain from the domains catalogue; the signature is its storage shape. What is known about it elsewhere is mostly recorded against the collections that enumerate it, and says so.
A carrier domain: the nominal type this object is stored and dispatched as.
Wikipedia
Multisetvia MultisetsSageMathsage.combinat.combinat.number_of_unordered_tuples(S, k)via Multisetsmathlib4MultisetSym (Fin n) kvia MultisetsMultiset: tuple<list<integer>, integer>