I compile mmdnn successful.
The code sudo python3 setup.py develop, it shows:

then when I sudo python3 tools/train.py configs/pascal_voc/ssd300_voc.py, it shows the error:

In my mmdetection/mmdet/ops/nms directory, it has no nms_cuda.

Solve the problem:
cd mmdet/ops/nms
python3 setup.py build_ext --inplace
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Solve the problem:
cd mmdet/ops/nmspython3 setup.py build_ext --inplace