code: def zero_grad(self, set_to_none=False):
      if self.opt_class is not None:
          self.optimizer_g.zero_grad(set_to_none)
          self.optimizer_d.zero_grad(set_to_none)
  
imports: import sys
  import torch
  import copy
  from hyperpyyaml import load_hyperpyyaml
  import speechbrain
  from speechbrain.utils.data_utils import scalarize
  import torchaudio
  import os
label_desc: Use image node_id 7 for calling the HifiGanBrain obj's underlying member method code with example usage: obj.zero_grad(set_to_none) without return types