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

Given a m x n binary matrix mat. In one step, you can choose one cell and flip it and all the four neighbors of it if they exist (Flip is changing 1 to 0 and 0 to 1). A pair of cells are called neighbors if they share one edge.
Return the minimum number of steps required to convert mat to a zero matrix or -1 if you cannot.
A binary matrix is a matrix with all cells equal to 0 or 1 only.
A zero matrix is a matrix with all cells equal to 0.
 
Please complete the following python code precisely:
```python
class Solution:
    def minFlips(self, mat: List[List[int]]) -> int:
```