code: def zero_grad(self):
      for v in self.models.values():
          v.zero_grad()
      for v in self.optimizers.values():
          v.zero_grad()
  
imports: import torch
  import tqdm
  from ..utils import common_functions
  from ..utils import loss_tracker
  from ..utils.key_checker import KeyChecker, KeyCheckerDict
label_desc: Use image node_id 9 for calling the BaseTrainer obj's underlying member method code with example usage: obj.zero_grad() without return types