code: def zero_grad(self):
      self.optimizer.zero_grad()
  
file_path: labml/helpers/labml_helpers/optimizer.py
imports: from typing import Tuple
  import torch
  from labml import tracker
  from labml.configs import BaseConfigs, option, meta_config
label_desc: Use image node_id 4 for calling the NoamOpt obj's underlying member method code with example usage: obj.zero_grad() without return types