@ptrblck l have an l update,
l hope that l fixed loading  state dic correctly. I did that as follow :
pretrained_dict=torch.load('model_best.pth.tar') 
pretrained_dict=pretrained_dict['state_dict']

then
net.load_state_dict(pretrained_dict)
net.fc2.register_forward_hook(get_activation('fc2'))

Until here it works fine without any error.
Can you confirm to me that with this process l load the pretrained weigh (best model) of net and not the initial random weight of net (used to initialize the network ?)
Then l did the following :
output = net(test_x[0], coord_test[0], adj_test[0], L_test[0],lmax_test[0],mask_test[0])
and l got the following error :
***** IndexError: invalid index to scalar variable.**
Thank you @ptrblck for you help