code: static <K, V> void populateMultimap(Multimap<K, V> multimap, ObjectInputStream stream)
        throws IOException, ClassNotFoundException {
      int distinctKeys = stream.readInt();
      populateMultimap(multimap, stream, distinctKeys);
    }
docs: Populates a multimap by reading an input stream, as part of deserialization. See {@link
  #writeMultimap} for the data format.