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

Given a string s, return the number of homogenous substrings of s. Since the answer may be too large, return it modulo 109 + 7.
A string is homogenous if all the characters of the string are the same.
A substring is a contiguous sequence of characters within a string.
 
Please complete the following python code precisely:
```python
class Solution:
    def countHomogenous(self, s: str) -> int:
```