Deduce the template parameter KEY from the value_type of the iterators supplied to the constructor of multiset. This deduction guide does not participate unless the specified ALLOC is convertible to bsl::allocator<KEY>.
Declared in <bslstl_multiset.h>
template<
class INPUT_ITERATOR,
class ALLOC,
class KEY = BloombergLP::bslstl::IteratorUtil::IterVal_t<INPUT_ITERATOR>,
class DEFAULT_ALLOCATOR = bsl::allocator<KEY>>
requires bsl::is_convertible_v<ALLOC *, DEFAULT_ALLOCATOR>
multiset<KEY>(
INPUT_ITERATOR,
INPUT_ITERATOR,
ALLOC*) -> multiset<KEY>;