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

You are given an integer array nums and an integer threshold.
Find any subarray of nums of length k such that every element in the subarray is greater than threshold / k.
Return the size of any such subarray. If there is no such subarray, return -1.
A subarray is a contiguous non-empty sequence of elements within an array.
 
Please complete the following python code precisely:
```python
class Solution:
    def validSubarraySize(self, nums: List[int], threshold: int) -> int:
```