Create a multiset having the same value as the specified original object. Use a copy of original.key_comp() to order the keys contained in this multiset. Use the allocator returned by 'bsl::allocator_traits<ALLOCATOR>:: select_on_container_copy_construction(original.get_allocator())' to allocate memory. This method requires that the (template parameter) type KEY be copy-insertable into this multiset (see {Requirements on KEY}).