Как двумерный массив разделить на 9 частей?

def validSolution(board):
    result = True
    for i in board:
        for j in i:
            if j == 0:
                result = False
 
    for i in range(1,10):
        for j in board:
            if j.count(i)>1:
                result = False
 
    for i in range(1,10):
        horline = []
        for j in range(len(board)):
            for k in range(len(board)):
                horline.append(board[k][j])
            if horline.count(i)>1:
                result = False
            line = []
 
 
    
 
 
    return result
 
print(validSolution([[5, 3, 4, 6, 7, 8, 9, 1, 2], 
                     [6, 7, 2, 1, 9, 5, 3, 4, 8],
                     [1, 9, 8, 3, 4, 2, 5, 6, 7],
                     [8, 5, 9, 7, 6, 1, 4, 2, 3],
                     [4, 2, 6, 8, 5, 3, 7, 9, 1],
                     [7, 1, 3, 9, 2, 4, 8, 5, 6],
                     [9, 6, 1, 5, 3, 7, 2, 8, 4],
                     [2, 8, 7, 4, 1, 9, 6, 3, 5],
                     [3, 4, 5, 2, 8, 6, 1, 7, 9]]))

grid = [[5, 3, 4, 6, 7, 8, 9, 1, 2],
        [6, 7, 2, 1, 9, 5, 3, 4, 8],
        [1, 9, 8, 3, 4, 2, 5, 6, 7],
        [8, 5, 9, 7, 6, 1, 4, 2, 3],
        [4, 2, 6, 8, 5, 3, 7, 9, 1],
        [7, 1, 3, 9, 2, 4, 8, 5, 6],
        [9, 6, 1, 5, 3, 7, 2, 8, 4],
        [2, 8, 7, 4, 1, 9, 6, 3, 5],
        [3, 4, 5, 2, 8, 6, 1, 7, 9]]
def list3x3(grid, row, col):
    row, col = 3 * row + 1, 3 * col + 1
    neighbors = [(row+i, col+j) for i in [-1, 0, 1] for j in [-1, 0, 1]]
    return [grid[x][y] for x, y in neighbors]
 
print list3x3(grid, 0, 2)

print list3x3(grid, 1, 1)

# main.shape == (9, 9)
main[0:3, 6:9]
main[3:6, 0:3]