docs: public synchronized void removeTimestamp(long ts) throws NoSuchElementException {
      Preconditions.checkState(!closed, "tracker closed ");
      Preconditions.checkState(allocationsInProgress > 0,
          "allocationsInProgress should be > 0 " + allocationsInProgress);
      Objects.requireNonNull(node);
      if (timestamps.remove(ts) == false) {
        throw new NoSuchElementException(
            "Timestamp " + ts + " was previously removed or does not exist");
      }
  
      allocationsInProgress--;
    }