Please solve the programming task below using a self-contained code snippet in a markdown code block.

You are given a 0-indexed array of unique strings words.
A palindrome pair is a pair of integers (i, j) such that:

0 <= i, j < words.length,
i != j, and
words[i] + words[j] (the concatenation of the two strings) is a palindrome.

Return an array of all the palindrome pairs of words.
You must write an algorithm with O(sum of words[i].length) runtime complexity.
 
Please complete the following python code precisely:
```python
class Solution:
    def palindromePairs(self, words: List[str]) -> List[List[int]]:
```