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

Given two strings s and t, determine if they are isomorphic.
Two strings s and t are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.
 
Please complete the following python code precisely:
```python
class Solution:
    def isIsomorphic(self, s: str, t: str) -> bool:
```