OpenCV cannot read manually edited YAML parameters

I manually add a custom matrix to a YAML file for openCV parameters, the problem is it cannot read the matrix and so OpenCV returns none-type. I do not know what is happening here as I tried editing both in notepad and visual studio code.

test_matrix: !!opencv-matrix
   rows: 2
   cols: 2
   dt: i
   data: [ 1, 1, 1, 1 ]
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