How to use a trained params to predict?

Hi. I am a new one here. It is a awesome lib for CV, thanks for your great work. Now, I am encountering a problem that I trained ssd_300_vgg16_atrous_voc on my own dataset, the dataset has 4 classes. After training, I got a "ssd_300_vgg16_atrous_voc_best.params" file. When I want to load the parmeters and predict on new images, it return an error, logs as it, AssertionError: Failed loading Parameter 'ssd0_convpredictor4_conv0_weight' from saved params: shape incompatible expected (126, 0, 3, 3) vs saved (30, 512, 3, 3) The command I used as follow, from gluoncv import model_zoo, data, utils from matplotlib import pyplot as plt import mxnet as mx ctx = [mx.cpu()] net = model_zoo.get_model('ssd_300_vgg16_atrous_voc', pretrained=False) net.load_parameters('ssd_300_vgg16_atrous_voc_best.params', ctx = ctx)

Thanks for any help.