Faster-rcnn.pytorch: ModuleNotFoundError: No module named 'datasets.factory'

[yiiiruu]

When I run the trainval_net.py I meet an error
Traceback (most recent call last):
File "/home/zyr/faster-rcnn.pytorch/trainval_net.py", line 28, in
from roi_data_layer.roidb import combined_roidb
File "/home/zyr/faster-rcnn.pytorch/lib/roi_data_layer/roidb.py", line 12, in
from datasets.factory import get_imdb
ModuleNotFoundError: No module named 'datasets.factory'

and I have __init__.py in my datasets dictionary.
can someone tell me what's the error?thank you

[yiiiruu]

add /lib dictronary to environment use:
export PYTHONPATH=/home/zyr/faster-rcnn.pytorch/lib
and it works