input: Write a function to solve a Sudoku puzzle by filling in the empty cells (represented by zeros) of the given board. The function should be able to solve any valid Sudoku puzzle if possible, and print the board if a solution exists. If no solution exists, it should print "No solution".
  assert solve_sudoku([
      [7,8,0,4,0,0,1,2,0],
      [6,0,0,0,7,5,0,0,9],
      [0,0,0,6,0,1,0,7,8],
      [0,0,7,0,4,0,2,6,0],
      [0,0,1,0,5,0,9,3,0],
      [9,0,4,0,6,0,0,0,5],
      [0,7,0,3,0,0,0,1,2],
      [1,2,0,0,0,7,4,0,0],
      [0,4,9,2,0,6,0,0,7]])==None
  # Expected output: Prints the solved Sudoku board
output: def solve_sudoku(board):
      def is_valid(board, row, col, num):
          for i in range(9):
              if board[row][i] == num or board[i][col] == num or board[3 * (row // 3) + i // 3][3 * (col // 3) + i % 3] == num:
                  return False
          return True
  
      def solve(board):
          for row in range(9):
              for col in range(9):
                  if board[row][col] == 0:
                      for num in range(1, 10):
                          if is_valid(board, row, col, num):
                              board[row][col] = num
                              if solve(board):
                                  return True
                              board[row][col] = 0
                      return False
          return True
  
      if solve(board):
          for row in board:
              print(row)
      else:
          print("No solution")