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

Given an array of positive integers arr, return the sum of all possible odd-length subarrays of arr.
A subarray is a contiguous subsequence of the array.
 
Please complete the following python code precisely:
```python
class Solution:
    def sumOddLengthSubarrays(self, arr: List[int]) -> int:
```