code: @Beta
    @SuppressWarnings("unchecked")
    // safe by specification of SortedSetMultimap.asMap()
    public static <K, V> Map<K, SortedSet<V>> asMap(SortedSetMultimap<K, V> multimap) {
      return (Map<K, SortedSet<V>>) (Map<K, ?>) multimap.asMap();
    }
docs: Returns {@link SortedSetMultimap#asMap multimap.asMap()}, with its type corrected from {@code
  Map<K, Collection<V>>} to {@code Map<K, SortedSet<V>>}.
  
  @since 15.0