See if passing the b_param retrieved as follows, to the optimizer, works:
x = torch.randn(1,10) # Dummy value!
ngpu = True # Dummy value!
nz = 100
ngf = 64
nc = 3
myGen = Generator(True, x)
shiftLayer = myGen.main[11] # I got the 11 by looking at the output of print(myGen) 
_, b_param = next(shiftLayer.named_parameters())
print(b_param)