code: def _create_and_populate_dummy_tarfile(fn):
      """Populate a dummy tarfile with dummy files."""
      fn.parent.mkdir(exist_ok=True, parents=True)
      with tarfile.open(fn, mode="x:gz") as tf:
          for i in range(3):
              with open(f"fci-rc{i:d}", "w"):
                  pass
              tf.addfile(tf.gettarinfo(name=f"fci-rc{i:d}"))
  
imports: from __future__ import annotations
  import contextlib
  import io
  import os
  import sys
  import tarfile
  import unittest
  from collections import defaultdict
  from unittest import mock
  import pytest
label_desc: Use image node_id 1 for calling a global function with example usage: _create_and_populate_dummy_tarfile(fn) without return types