`UnmodifiableMultimap.forEach` uses the `Multimap.forEach` default implementation which involves listing entries, and creating a new lambda instead of simply passing the BiConsumer through to the protected instance. This is safe to pass directly though because `forEach(BiConsumer)` is a read-only operation.
Multiset<K> createKeys() {
      return fromMultimap.keys();
    }
    @Override
    public boolean put(K key, V2 value) {
      throw new UnsupportedOperationException();
    }
    @Override
    public boolean putAll(K key, Iterable<? extends V2> values) {
      throw new UnsupportedOperationException();
    }
    @Override
    public boolean putAll(Multimap<? extends K, ? extends V2> multimap) {
      throw new UnsupportedOperationException();
    }
    @SuppressWarnings("unchecked")
    @Override
    public boolean remove(Object key, Object value) {
      return get((K) key).remove(value);
    }
    @SuppressWarnings("unchecked")
    @Override
    public Collection<V2> removeAll(Object key) {
      return transform((K) key, fromMultimap.removeAll(key));
    }
    @Override
    public Collection<V2> replaceValues(K key, Iterable<? extends V2> values) {
      throw new UnsupportedOperationException();
    }
    @Override