.modules() also returns pretrained_model as one of the elements.
For example see:
list(nn.Sequential(nn.Linear(10, 20), nn.ReLU()).modules())
Out[9]:
[Sequential (
   (0): Linear (10 -> 20)
   (1): ReLU ()
 ), Linear (10 -> 20), ReLU ()]

In [10]: list(nn.Sequential(nn.Linear(10, 20), nn.ReLU()).children())
Out[10]: [Linear (10 -> 20), ReLU ()]