I have cleared all the test cases but still scored 0/100
Below mentioned is the error:
Comment line with index: UNQ_C1 wasn’t found in code
Please help me with the issue??
That must mean you have accidentally removed one of the comment lines in that function cell that the grader depends on. In general, you should be careful not to modify things outside of the “YOUR CODE HERE” blocks. It’s not illegal to do that, but you need to be careful. Your best bet is to get a clean copy of that notebook and then carefully “copy/paste” over just your completed code. There is a topic about how to do that on the DLS FAQ Thread.
The beginning of the template code for yolo_filter_boxes should look like this:
# UNQ_C1 (UNIQUE CELL IDENTIFIER, DO NOT EDIT)
# GRADED FUNCTION: yolo_filter_boxes
def yolo_filter_boxes(boxes, box_confidence, box_class_probs, threshold = .6):
They weren’t kidding when they said “DO NOT EDIT” there. 
Note that the other way you can get this problem is by copying an old solution off the Internet. They changed things quite a bit in April 2021: not just the mechanics like how the grader works, but also the definitions of some of the APIs. So you can’t just copy old code and expect it to work. Of course it’s cheating if you copied someone else’s code, but it also doesn’t work if you started on the course a long time ago and are using your own code from before April 2021. In the latter case, you need to actually read the definitions carefully to see what changed.