int idx = fieldName.lastIndexOf('.');
                if (idx >= 0) {
                    fieldName = fieldName.substring(idx + 1);
                    key = fieldName;
                }

                if (fieldName.endsWith("]")) {
                    key = fieldName.substring(fieldName.lastIndexOf('[') + 1, fieldName.length() - 1);
                    try {

      synchronized (mutex) {
        return delegate().indexOf(o);
      }
    }

    @Override
    public int lastIndexOf(@CheckForNull Object o) {
      synchronized (mutex) {
        return delegate().lastIndexOf(o);
      }
    }

    @Override
    public ListIterator<E> listIterator() {
      return delegate().listIterator(); // manually synchronized
    }

      synchronized (mutex) {
        return delegate().indexOf(o);
      }
    }

    @Override
    public int lastIndexOf(@CheckForNull Object o) {
      synchronized (mutex) {
        return delegate().lastIndexOf(o);
      }
    }

    @Override
    public ListIterator<E> listIterator() {
      return delegate().listIterator(); // manually synchronized
    }