It provides the operations described in the
preceding requirements table for equivalent keys; that is, an
unordered_multiset
supports the
a_eq operations in that table, not the
a_uniq operations
. For an
unordered_multiset<Key> the
key_type and the
value_type are
both
Key. The
iterator and
const_iterator types are both
constant iterator types
. It is unspecified whether they are the same type
.