YoloV3 from lightnet 1.1.1 : wrong data type in _regionloss.py

Trying to use YoloV3 from lightnet 1.1.1 on my custom dataset, the package threw me the following error :

Exception has occurred: AttributeError
'list' object has no attribute 'data'
  File "C:\some\path\lightnet\network\loss\_regionloss.py", line 97, in forward
    nB = output.data.size(0)

indeed output is a list. Isn't it because somewhere output[0] should be performed ?

EDIT

looking further, I see that at the beginning of the call i.e. in process_batch of the training engine, out is a list that I assume should get flatten by line 489 of module.py from PyTorch (base class that I suppose defines the loss method) :

result = self.forward(*input, **kwargs)

but somehow the input (that I assume should be a list) got encapsulated in a tuple and this may be what causes the error ?