It does not work for this sudoku for example :

[[5 3 4 6 7 8 9 2 2]
[6 7 2 2 9 5 3 4 8]
[2 9 8 3 4 2 5 6 7]
[8 5 9 7 6 2 4 2 3]
[4 2 6 8 5 3 7 9 2]
[7 2 3 9 2 4 8 5 6]
[9 6 2 5 3 7 2 8 4]
[2 8 7 4 2 9 6 3 5]
[3 4 5 2 8 6 2 7 9]]

I replaced all 1s in a valid sudoku by 2s.