OpenCV(3.4.3) /opt/opencv_contrib/modules/ximgproc/src/structured_edge_detection.cpp:432: error: (-215:Assertion failed) modelFile.isOpened() in function 'StructuredEdgeDetectionImpl' code example

Example: error: (-215:Assertion failed) !_src.empty() in function 'cv::cvtColor'

This error happened because the image didn't load properly.
So you have problem with the previous line cv2.imread my suggestion is :

check if the images exist in the path you give

check the count variable if he have valid number