code: def step(self):
      rate = self.rate(tracker.get_global_step() / self.step_factor)
      for p in self.optimizer.param_groups:
          p["lr"] = rate
      self._rate = rate
      self.optimizer.step()
  
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 2 for calling the NoamOpt obj's underlying member method code with example usage: obj.step() without return types