code: def step(self, closure=None):
      loss = self._base_optimizer.step(closure)
      for group in self._base_optimizer.param_groups:
          group["lookahead_step"] += 1
          if group["lookahead_step"] % group["lookahead_k"] == 0:
              self.update_slow(group)
      return loss
  
file_path: pytorch-image-models/timm/optim/lookahead.py
imports: from collections import OrderedDict
  from typing import Callable, Dict
  import torch
  from torch.optim.optimizer import Optimizer
  from collections import defaultdict
label_desc: Use image node_id 4 for calling the Lookahead obj's underlying member method code with example usage: obj.step(closure) and returns: loss