code: def _make_oasis_data(dartel=True):
      n_subjects = 457
      prefix = "mwrc" if dartel else "mwc"
      ids = pd.DataFrame(
          {"ID": [f"OAS1_{i:04}" for i in range(n_subjects)]}
      ).to_csv(index=False, sep="\t")
      data = {
          "oasis_cross-sectional.csv": ids,
          "data_usage_agreement.txt": "",
      }
      path_pattern = str(
          Path(
              "OAS1_{subj:04}_MR1",
              "{prefix}{kind}OAS1_{subj:04}_MR1_mpr_anon_fslswapdim_bet.nii.gz",
          )
      )
      for i in range(457):
          for kind in [1, 2]:
              data[
                  path_pattern.format(subj=i, kind=kind, prefix=prefix)
              ] = ""
      return dict_to_archive(data)
  
file_path: nilearn/nilearn/datasets/tests/test_struct.py
imports: from pathlib import Path
  import numpy
  import pandas
  import pytest
  from nibabel import Nifti1Image
  from nilearn.datasets import struct
  from nilearn.datasets.tests._testing import dict_to_archive, list_to_archive
label_desc: Use image node_id 2 for calling a global function with example usage: _make_oasis_data(dartel) and returns: dict_to_archive