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.
We say that an integer x is expressible from nums if there exist some integers 0 <= index1 < index2 < ... < indexk < nums.length for which nums[index1] | nums[index2] | ... | nums[indexk] = x. In other words, an integer is expressible if it can be written as the bitwise OR of some subsequence of nums.
Return the minimum positive non-zero integer that is not expressible from nums.
 
Please complete the following python code precisely:
```python
class Solution:
    def minImpossibleOR(self, nums: List[int]) -> int:
```