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

Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 (e.g.,"waterbottle" is a rotation of"erbottlewat"). Can you use only one call to the method that checks if one word is a substring of another?
Please complete the following python code precisely:
```python
class Solution:
    def isFlipedString(self, s1: str, s2: str) -> bool:
```