code: def _get_unique_cpu_bases(images: List[Config]) -> Set[CpuBase]:
      bases = set()
      for x in images:
          if x.get("gpu") is not None:
              continue
          bases.add(
              CpuBase(base_image=x["base_image"], python=x["python"])
          )
  
      return bases
  
imports: from absl import flags, app, logging
  from copy import copy
  from typing import Dict, List, Any, NamedTuple, Optional, Set
  from enum import Enum
  import json
  import pprint
label_desc: Use image node_id 4 for calling a global function with example usage: _get_unique_cpu_bases(images) and returns: bases