docs: protected void offerAt(final int pos, O e) {
      if(pos == NO_VALUE) {
        // resize when needed
        if(size + 1 > queue.length) {
          resize(size + 1);
        }
        index.put(e, size);
        size++;
        heapifyUp(size - 1, e);
        heapModified();
        return;
      }
      assert (pos >= 0) : "Unexpected negative position.";
      assert (queue[pos].equals(e));
      // Did the value improve?
      if(comparator.compare(e, queue[pos]) >= 0) {
        return;
      }
      heapifyUp(pos, e);
      heapModified();
      return;
    }