docs: private int heapifyUp(HeapEntry<E> entry) {
      int numSwaps = 0;
      while (true) {
        if (entry.index == 0) {
          break;
        }
        HeapEntry<E> parentEntry = parent(entry);
        if (compare(entry, parentEntry) >= 0) {
          break;
        }
        numSwaps++;
        swap(entry, parentEntry);
      }
      return numSwaps;
    }