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

You are given a 0-indexed integer array nums and a positive integer k.
You can apply the following operation on the array any number of times:

Choose any subarray of size k from the array and decrease all its elements by 1.

Return true if you can make all the array elements equal to 0, or false otherwise.
A subarray is a contiguous non-empty part of an array.
 
Please complete the following python code precisely:
```python
class Solution:
    def checkArray(self, nums: List[int], k: int) -> bool:
```