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

A wonderful string is a string where at most one letter appears an odd number of times.

For example, "ccjjc" and "abab" are wonderful, but "ab" is not.

Given a string word that consists of the first ten lowercase English letters ('a' through 'j'), return the number of wonderful non-empty substrings in word. If the same substring appears multiple times in word, then count each occurrence separately.
A substring is a contiguous sequence of characters in a string.
 
Please complete the following python code precisely:
```python
class Solution:
    def wonderfulSubstrings(self, word: str) -> int:
```