sudoku solver python

To do this, write a function sudoku_solver (s). Call parameter: A string s of length 81 with the digits 0-9. This contains the columns of an unresolved Sudokus without spaces written behind each other. Where 0 is an unfilled field. Feedback: The solved sudoku as a string in the format above. >>> sudoku_solver ( ' 00401308763190852490745261350618037919873504674020080137584910 2802367495060021030 ' ) '254613987631978524987452613526184379198735246743296851375849162812367495469521738 ' >>> sudoku_solver ( ' 00875026354736009062301807080920143575103692823489561707254910 0006123759095007342 ' ) '918754263547362891623918574869271435751436928234895617372549186486123759195687342 ' >>> sudoku_solver ( ' 68395240710543682990080103559038417680010759030756028403104596 8468203751059608002 ' ) '683952417175436829924871635592384176846127593317569284231745968468293751759618342 ' >>> sudoku_solver ( ' 06000030040070000000000008000000801250060000000000005008200070 0000500600000010000 ' ) '961845327458723169237169584796358412524691873813274956182436795379582641645917238 ' the program must solve the last example in less than 5 minutes