@J2ktIncompatible
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
    stream.defaultReadObject();
    int distinctElements = Serialization.readCount(stream);
    setBackingMap(new HashMap<>());
    Serialization.populateMultiset(this, stream, distinctElements);
  }

  @GwtIncompatible @J2ktIncompatible private static final long serialVersionUID = 0;