AttributeError: 'HybridSequential' object has no attribute 'bias'

[ChessQian]

Hi, it occured a bug like that:
Traceback (most recent call last):
File "train_cascade_rcnn.py", line 506, in
net = get_model(net_name, pretrained_base=False)
File "C:\Users\vis\Miniconda3\envs\cascade\lib\site-packages\gluoncv-0.3.0-py3.7.egg\gluoncv\model_zoo\model_zoo.py", line 120, in get_model
File "C:\Users\vis\Miniconda3\envs\cascade\lib\site-packages\gluoncv-0.3.0-py3.7.egg\gluoncv\model_zoo\cascade_rcnn\cascade_rcnn.py", line 510, in cascade_rcnn_resnet50_v1b_voc
File "C:\Users\vis\Miniconda3\envs\cascade\lib\site-packages\gluoncv-0.3.0-py3.7.egg\gluoncv\model_zoo\cascade_rcnn\cascade_rcnn.py", line 346, in get_cascade_rcnn
File "C:\Users\vis\Miniconda3\envs\cascade\lib\site-packages\gluoncv-0.3.0-py3.7.egg\gluoncv\model_zoo\cascade_rcnn\cascade_rcnn.py", line 92, in init
File "C:\Users\vis\Miniconda3\envs\cascade\lib\site-packages\gluoncv-0.3.0-py3.7.egg\gluoncv\model_zoo\rcnn\rcnn2.py", line 76, in init
AttributeError: 'HybridSequential' object has no attribute 'bias'

So, how can I fix it?