Bug Report for quickSort

[robskrob]

Bug Report for https://neetcode.io/problems/quickSort

The exercise is telling me that my submission is wrong.My solution is also "stable" unintentionally. Here is my code for quick sort:

class Pair:
    def __init__(self, key: int, value: str):
        self.key = key
        self.value = value
        
class Solution:
    def quickSort(self, pairs):
        lastIndex = len(pairs) - 1

        left = []
        right = []

        if lastIndex == -1:
            return pairs

        pivot = pairs[lastIndex]

        for i in pairs[0:lastIndex]:
            if i.key <= pivot.key:
                left.append(i)
            else:
                right.append(i)

        return self.quickSort(left) + [pivot] + self.quickSort(right)

Is there something wrong with my code that fails to meet the requirements? I believe that my solution sorts the list correctly.

Given a list of key-value pairs, sort the list by key using Quick Sort. For each partitioning step:

1. Use the right-most element as the pivot.
2. Elements less than the pivot should be placed to the left of the pivot, and elements greater than or equal to the pivot should be placed to the right of the pivot.