code: def fields(self):
      return chain.from_iterable(op.fields() for op in self.objects)
  
imports: import re
  from dataclasses import dataclass, InitVar, field
  from itertools import chain
  from typing import Any, Dict, List, Union, Optional, ClassVar
  import numpy
  from toolz import valfilter, valmap
label_desc: Use image node_id 2 for calling the Stack obj's underlying member method code with example usage: obj.fields() and returns: chain