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

You are given a string s consisting only of letters 'a' and 'b'. In a single step you can remove one palindromic subsequence from s.
Return the minimum number of steps to make the given string empty.
A string is a subsequence of a given string if it is generated by deleting some characters of a given string without changing its order. Note that a subsequence does not necessarily need to be contiguous.
A string is called palindrome if is one that reads the same backward as well as forward.
 
Please complete the following python code precisely:
```python
class Solution:
    def removePalindromeSub(self, s: str) -> int:
```