docs: private void readObject(ObjectInputStream s)
      throws IOException, ClassNotFoundException {
      int size, expectedMaxSize;
      Object o;
  
      expectedMaxSize = s.readInt();
      size = s.readInt();
  
      map = new IdentityHashMap<E, Boolean>(expectedMaxSize);
      for (int i = 0; i < size; i++) {
        o = s.readObject();
        internalAdd(ErasureUtils.<E>uncheckedCast(o));
      }
    }