code: def generate_col_names():
      # 'a', 'b'... 'z', then 'aa', 'ab'...
      letters = string.ascii_lowercase
      yield from letters
      for first in letters:
          for second in letters:
              yield first + second
  
imports: from collections import OrderedDict
  from decimal import Decimal
  import io
  import itertools
  import json
  import string
  import unittest
  import numpy
  import pytest
  import pyarrow
  from pyarrow.json import read_json, ReadOptions, ParseOptions
label_desc: Use image node_id 1 for calling a global function with example usage: generate_col_names() without return types