code: def few_surfaces(monkeypatch):
      """Set the _MNE_FEW_SURFACES env var."""
      monkeypatch.setenv("_MNE_FEW_SURFACES", "true")
      yield
  
imports: import os
  from functools import reduce
  from glob import glob
  from shutil import copyfile
  import numpy
  import pytest
  from numpy.testing import assert_allclose, assert_array_almost_equal, assert_array_equal, assert_array_less
  import mne
  from mne._fiff.constants import FIFF
  from mne.channels import DigMontage
  from mne.coreg import Coregistration, _is_mri_subject, coregister_fiducials, create_default_subject, fit_matched_points, get_mni_fiducials, scale_labels, scale_mri, scale_source_space
  from mne.datasets import testing
  from mne.io import read_fiducials, read_info
  from mne.source_space import write_source_spaces
  from mne.transforms import Transform, _angle_between_quats, apply_trans, invert_transform, read_trans, rot_to_quat, rotation, scaling, translation
  from mne.utils import catch_logging
label_desc: Use image node_id 1 for calling a global function with example usage: few_surfaces(monkeypatch) without return types