code: @Override
    public ImmutableList<V> get(@NullableDecl K key) {
      // This cast is safe as its type is known in constructor.
      ImmutableList<V> list = (ImmutableList<V>) map.get(key);
      return (list == null) ? ImmutableList.<V>of() : list;
    }
docs: Returns an immutable list of the values for the given key. If no mappings in the multimap have
  the provided key, an empty immutable list is returned. The values are in the same order as the
  parameters used to build this multimap.