Added warning message when --single-cls
is used incorrectly by [#13028](https://github.com/ultralytics/yolov5/issues/13028)
#12978
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6m 32s | |
3m 28s | |
10m 26s | |
6m 40s | |
2m 26s | |
2s | |
29m 34s |