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

Given a string of digits s, return the number of palindromic subsequences of s having length 5. Since the answer may be very large, return it modulo 109 + 7.
Note:

A string is palindromic if it reads the same forward and backward.
A subsequence is a string that can be derived from another string by deleting some or no characters without changing the order of the remaining characters.

 
Please complete the following python code precisely:
```python
class Solution:
    def countPalindromes(self, s: str) -> int:
```