torch.optim.Optimizer.add_param_group
Optimizer.add_param_group(param_group)
Add a param group to the "Optimizer" s param_groups.
This can be useful when fine tuning a pre-trained network as frozen
   layers can be made trainable and added to the "Optimizer" as
   training progresses.
Parameters:
      param_group (dict) -- Specifies what Tensors should be
      optimized along with group specific optimization options.