How to show lines and images on a chess board (matrix_plot)

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Hi, I naively created a chess board with a matrix_plot.

m = matrix_plot([[1,0,1,0,1,0,1,0],
                 [0,1,0,1,0,1,0,1],
                 [1,0,1,0,1,0,1,0],
                 [0,1,0,1,0,1,0,1],
                 [1,0,1,0,1,0,1,0],
                 [0,1,0,1,0,1,0,1],
                 [1,0,1,0,1,0,1,0],
                 [0,1,0,1,0,1,0,1],
                 [1,0,1,0,1,0,1,0]]
                  )

Shown alone, it looks almost like a chess board, but it has axes and white padding on the periphery

 (m).show(aspect_ratio=1)

I then naively tried to add a line to that plot -

Q = line([(-0.5,0),(1,1)])
(m+Q).show()

Somehow I have lost the whole matrix plot . This is version 8.7 in a jupyter notebook

Q = line([(-0.5,0),(1,1)])
(m+Q).show()

i only get 2 rows - the rest is truncated.

Question - how to graph lines on top of this matrix plot without truncating the apprearance?

Merci! Pat